Which Pokemon is most worthy of a charged TM.

No brainer, TTar. Given the current raid boss landscape, you might consider using a Fast TM on the Golem (assuming you have some RT/SE you're happy with).

In general, I prefer planning for Fast TM changes over Charge because:
1 - You know what you're going to get for sure, unless you're dumping a legacy move.
2 - Fast TMs are more common.

1. Tyranitar
2. Golem
3. Espeon

You may want to keep that Espeon as a defender, although defenders haven't much use now. I have a C/PB Espeon but may just keep him as is.

Assuming all those are high level mons I would TM the Golem to RT/RB/SE.

I would wait for a higher IV Tyranitar from a raid. You may get one that's B/SE/C, unless your current Tyranitar is already at level 30 or above.

Golem, then Tyranitar. No Espeon, just evolve another one.
Anyway, the only thing wrong with Fire Blast is its fire typing.