1. Not very valuable. Handling and storage costs far outweigh acquisition costs.
2. Unmatched, easy; well matched, somewhat difficult.
3. Generally it depends on the specific inherited immune characteristics of mother and child, similar to these factors in kidney donation.
4. For decades, yes, for a lifetime no.
5/6 No and sort of yes.
If you are going to donate cord blood for others, as a humanitarian thing, check with your OB/GYN about whether they know who would need to be there to ship the donation.
If you are going to save it for family use, I would do so only if you are aware of a known risk requiring use of such a donation in the baby or family, such as an inherited blood disorder or similar risk factor. If there is none, the cost-effectiveness of banking with a commercial outfit is poor unless you have inexpensive access to a liquid nitrogen-level freezer for long term storage. If the family has such an inherited disorder, check with the physicians treating it for instructions.
One source I looked at was: https://parentsguidecordblood.org/en
If you're trying to be homo economicus and maximize your expected utility, probably it's not worth it. But if you're not, you can still do it! We did (blood and tissue).