a bunch of eevee questions?

High IV is less of a concern now...I evolved/leveled a Lvl 2 Chancey -> max Blissey (37.5) , but that was when CP was a thing and defenders mattered...

Defenders don't matter at all IMO and I wouldn't powerup or use TMs on them now (not even my Zh/Psychic Blissey).

At this point, unless you are rolling in dust, it maybe better to try to catch a higher level, higher IV one or just wait...

I'd turn the level 20 one to Espeon if you need more Psychic attackers.

Oops, noticed your Vap was WP...I'd probably just leave it since it's still a water/STAB move and very high level...move rework can change everything so who knows...

No need to rush to use resources at least.

1
2 no, not when eevees are super rare.
3 make it an espeon, only 6%. difference isnt worth choosing the level 3. Vaporeon, flareon and jolteon can be catched in raids.
4 would only use tm, garantueed better movese and cp doesnt matter anymore. With hp a good attacker into tyrannitar.

1
Hatch more 5 kilometer eggs.
2
No, you probably don't have the candies.
3
Evolve.
4
Yes, Water Pulse is really the worst move possible for Vaporeon overall. Charged TM it if you have one.
5
Then use the name trick on the 91% one.

1, 2) How many gyms are near you? (Enough to complete a few raids and get a TM, obviously.) Do you have another player you can do tier 3 raids with? Watch https://gymhuntr.com for tier 3 raids and hope for some good IV level 20 Eeveelutions. Wait on to the level 3 Eevee for now.
3, 5) If you need a good Espeon still, then go for it. (And you can do the walking method for guaranteed Espeon or Umbreon if you don't want to use the name.) Otherwise you might just save this for later and look for some raids for the original three Eeveelutions.
4) Water Pulse is Vaporeon's worst charge move, so using a TM would only make it better. Look for some Vaporeon raids first though. If TMs seem to be more common than Eeveelutions, then use a charge TM on this Vaporeon.