Power up 100% feebas / raikou / eevee + 96% tyranitar?

Save the eevee for gen IV's release with glaceon

Dont do anything with the raikou, electric isnt overly relevant, it is very low leveled so it will take a lot of investment to make it usable and Smack down tyrantiar handles flying types better and doesnt cost rarecandy, plus magnazone and electavire are coming when gen IV does that also dont need rarecandy

I'd walk the feebas, but not evolve it yet, Milolitic a good tanky water attacker, think gyarados with more defense but less attack

I evolved only the ones to get a fullset of shiny evolutions, the rest im saving for gen IV and VI. If you TM off last resort, you will never get it back.

You got a 100% Raikou and its not maxed out??? Crazy..

Max out both the Feebas and Tyra! 50% discount on dust, doesn't get better than that.

(a) 100% Raikou is worth maxing out. Yes, it'll cost rare candy, but perfect IV useful Legendaries are worth the rare candy. Top attacker against several pokemon often seen in gyms (Gyarados, Vaporeon, Milotic etc.)

(b) Perfect Feebas is also worth maxing out in my eyes, but I would wait until you got enough candies without having to walk it more than the mandatory 20 km. Milotic is one of six Pokemon that belong in a perfect Gym lineup at the moment.

(c) Either go for Espeon or hold on to it until future generations. Espeon is near the top for Psychic DPS while the other Eevolutions are outclassed by other options. (Jolteon and Flareon only by legendaries so far, but still.)

(d) Espeon with Last Resort is #1 neutral DPS in cloudy weather, for what it's worth. I still only consider it a trophy and wouldn't waste a really good Eevee or too much stardust on it.

(e) 13 att is a bummer, but since it's your best Smack Down Tyra and Lucky to boot I say max it out.

It all comes down to what you like.

If you like to power up that 100% Raikou, do so but it won't get you much use in upcoming legendary raids (during Regirock it'll help you with T3 and possibly T4 raids). Given that you also have 2 powered up already, there just isn't much need to powering up a third.

A Milotic is a decent defender. Not good, not bad, just decent. I personally wouldn't invest in it even if my town was fast gym turnover. Again, if you like to boost 100% Pokemon, do it as it's 50% discount.

There are two Eeveelutions that might be useful for you: Espeon can greatly assist you in Machamp solo's, but I don't know whether you are already capable of doing so. Glaceon could become the strongest ice type in the game if Mamoswine gets lackluster moves. Should Rayquaza come back for its shiny round after the release of Glaceon, you'll have yourself a fancy top counter.

Tyranitar are always useful and for the upcoming, predicted, Moltres day, they are the top counter. However, I wouldn't power it up as I only used up to 3 Tyranitar for Articuno and would probably not use more than 3 for Moltres either.

Out of all that you mentioned, Tyranitar is your best bet but none are needed in the current and next raid boss rotation. So if I were you, I'd save up (I power up counters for legendaries when they become available and nothing more).

1.) A 100% legendary - particularly a powerful one like Raikou - pretty much demands being maxed out. Depending on your rare candy supply, the difference between a level 15 legendary and level 20 really isn't all that much - 20 candy and 21.4k dust. Given how much dust you have, the 21k difference is pretty negligible.

2.) Again, candy is your biggest hangup here. To power up from 1 to 40 costs 304 candy before factoring evolution costs, whereas your level 30 to max takes 182. I personally have no need to power up defenders but if you want an extra something to toss in gyms that isn't Blissey or Snorlax then you do you. On the topic of dust, it's actually less to max out a level 1 lucky than a level 30 regular - 135k dust vs 150k dust respectively.

3.) Either Espeon or save it for a future Eeveelution. Depends on what you need IMO, I'd rather lean towards one of the Eeveelutions I have some control over.

4.) I'm saving mine. Last Resort is a novelty and I already have one of each non-shiny that knows it. If you CTM it and lose it you can't get it back.

5.) See points 1 and 2 about candy. I've found dust cost to be a non-issue for my luckies, and I'm someone who normally struggles with dust management.