I've been researching this topic in my spare time and would be happy to help. Do you have time to clarify a few points? Here are some thoughts and questions that came up as I reviewed your post:

1. Livestock vs. Wild Birds
   The distinction between livestock and wild birds is significant. Livestock are in much closer contact with humans and are biologically closer as well. How granular of an analysis are you interested in here?
2. US-specific H5N1 Trends
   It's peculiar that H5N1 seems so prevalent in the US. Could this be due to measurement bias, or does the US simply have more factory farming? How interested are you in exploring the reasons behind this trend?
3. Citations and Depth
   While most points aren’t cited (which is fine), it might be valuable to compile both a list of key aspects and resources for further reading. Are you looking for a more polished, thoroughly cited document?
4. Biological Factors of Severity
   Binding to human receptors is just one factor controlling the severity and infectiousness of a virus. Would you like a deeper dive into the biology of respiratory infections and what makes them dangerous?
5. Tamiflu and Xofluza
   Wikipedia notes that Tamiflu has limited evidence of being worth the side effects. Are you interested in a detailed evaluation of its effectiveness? Similarly, how interested are you in assessing the likelihood of shortages and efficacy of Tamiflu/Xofluza during an H5N1 pandemic?
6. Over-the-counter Tests
   Is the issue a lack of over-the-counter tests specifically for H5N1, or for flu in general? General flu PCR testing is likely available—should we investigate this?
7. Trajectory of Illness
   For past H5N1 cases, is there a treatable "window of opportunity" before the infection becomes severe? How critical is it to determine whether mild cases might escalate and require aggressive intervention?
8. Historical Epidemics
   I could pull together a list of relevant modern epidemics (human-to-human airborne transmission without an animal vector). Are there any specific criteria you'd like to prioritize?
9. Cross Immunity
   While cross immunity seems important, determining decision-relevant information may be challenging. Would you like a summary of existing knowledge or only actionable insights?
10. Respiratory Infection Dynamics
    Epidemiologists suggest that respiratory infections are deadlier lower in the lungs but more infectious higher in the system. Is this a fundamental tradeoff? Would a "both-and" virus be possible? What evolutionary advantages might viruses have in infecting the lower lungs?
11. Government Stockpiles and Interventions
    What stockpiles of H5N1 vaccines exist? What options are available for increasing testing and vaccination of livestock? How are governments incentivizing medication, vaccine, and PPE production?
12. Political Considerations
    Should we examine how a Trump presidency or similar political scenarios might influence the interaction between local and federal health agencies?
13. Species-to-Species Spread
    The rapid spread of H5N1 to multiple bird and mammal species raises the question of whether humans will inevitably be affected. Is this worth exploring in-depth?
14. Mortality and Long-term Effects
    What demographics do other flu strains tend to affect most? Are there long-term side effects comparable to "long COVID"?
15. Mutation and Vaccine Efficacy
    How quickly do flu strains, especially H5N1, tend to mutate? What implications does this have for vaccine efficacy and cross-reactivity? How much asymptomatic spread occurs with flu, and how long does it remain airborne?
16. No Deaths Yet
    How should we update based on the fact that, contrary to past occurrences of H5N1 that had a ~50% CFR, none of the 58 confirmed cases have died?

Finally, I’d be interested to hear which of these questions or areas you find most compelling. Are there other questions or directions you’d like to explore? This will help me prioritize my efforts.

Epidemic Scares That Did Not Pan Out

• 1976 - Legionnaires' Disease: Initially alarming but identified as a bacterial infection treatable with antibiotics. (Not relevant: bacterial)
• 2001 - Anthrax Attacks: Bioterrorism-related bacterial outbreak causing fear but limited deaths. (Not relevant: bacterial)
• 2005 - Avian Flu (H5N1): No confirmed US human cases despite global fears. (Relevant)
• 2014 - Ebola: Strict public health measures limited US cases to three. (Relevant)
• 2016 - Zika Virus: Local transmission limited to parts of Florida and Texas. (Not relevant: mosquito vector)

I am no biologist but I thought it would be fun to give it a try. Hoping it's not too late to participate.
For the purpose of this experiment, I assumed everything written in sound scientific papers was right, as I had neither the time nor the knowledge to do a proper truth-check.

Here is what I found :  

The fact that we see very few human cases compared to what we could expect for a virus which can become human-compatible with a single point mutation could be partially explained by the heterogeneity of the mutation rate over the genome:

•  in this paper, a 1 to 100 ratio of mutation rate inside the human genome is mentioned : https://pubmed.ncbi.nlm.nih.gov/35218359/
     There are known factors which hints at a low / large mutation rate for a sequence, so one could investigate further whether this would be the case for the "single point mutation" mentioned
  -> you can divide the probability by 100 in the best case

A paper where they infect ferret with H5N1 and test how to mutate the genome to make it airborne:

• https://pmc.ncbi.nlm.nih.gov/articles/PMC4810786/
• "Four amino acid substitutions in the host receptor-binding protein hemagglutinin, and one in the polymerase complex protein basic polymerase 2, were consistently present in airborne-transmitted viruses."

As an alternative to tamiflu which can also be used in combination with it : favipiravir

• https://www.sciencedirect.com/science/article/pii/S0163725820300401, a 2020 paper about it
• licensed as an influenza drug in Japan
• when used in combination with tamiflu, a 2020 paper (with small sample size = 40) suggests that combining tamiflu with favipiravir improve significantly the efficiency
• as it has been envisioned as a drug against COVID, it's easy to find meta-analyses on the side-effects of this drug
• a huge problem with tamiflu is that the influenza viruses develop resistance to it. favipiavir does not seem to have this problem

What percent of cows in infected dairy herds were actually sick?

According to AVMA, less than 10%: link. It looks like that's only the symptomatic animals though, so your answer might depend on how you define "actually sick."

How did H5N1 spread from bird to cow if it requires fluids?

Cows occasionally eat birds. That might do it.

What does it need to get airborne?

I'm not sure this is the right question: as I understand it, the flu generally spread on fluids (mainly saliva), and if the droplets are small enough (< 5μm diameter), they get classified as aerosols and called airborne.

Qn: Could you clarify the intended audience and final use case for this research? It would help to choose between technical depth/accessibility/level of supporting info.

Additional major epidemics or scares that didn’t pan out ($50 for first few, $25 for later)

2014-15 HPAI outbreak in the US, which didn't ultimately make it to humans

“Xofluza is more effective than Tamiflu but I can’t find anywhere to buy it online”

• Both drugs are prescription-only medications so you would need a valid prescription to access it. Telehealth would suffice for prescription and online pharmacies can home deliver. 

If I get more time later today I will update this comment.