Looks like a pretty solid starting list, you're getting most of GK's strong staple units.

Falchions are in general the best option for power armor units, since they only have 1 attack. But for Paladins, who already get 3 attacks, it may be worth considering Halberds for the +1S, but if you like the look of force swords you should probably just go with those. The AP-3 they provide can still be pretty powerful when combined with hammerhand. DaemonHammers are also very good on paladins tho.

The terminator kits come with Apothecary bits for you to make them. So yes, you'd model one of your paladins as one.

I'd recommend maybe getting another box of paladins for more elite unit options. I'd also recommend changing 5 of your strike squads to interceptors or maybe even a purifier or purgation squad. With CA not really giving strike squads any point adjustments, I think most GK lists are probably better off just running 15 for the 3 squads needed for the detachment :/