Yes Gabriel Angelos is in power armour, Mark 7 I believe. He starts out armed with a power sword and bolt pistol. As I recall during the campaign you can upgrade him to have a Thunder Hammer. But, no he doesn't end up wearing Terminator Armour - not sure why the Forgeworld Model has him in that (unless that comes from DoW2 or
DoW 3?)
Not sure what mace you're referring to.
Bale has a power scythe. Been a long while since I've played
DoW though.
You can see what Sindri looks like
here Gabriel Angelos's details are noted
here I'm pretty sure there's no models you can just use OOB, and most will need kitbashing, maybe even some scratchbuilding of details, although I can't really offer up any examples to start with, looking at
GW's current range I don't think there are any that would make an easy starting point if you're aiming for accuracy compared to the game's models.
For Bale I'd go with the Chaos Lord in power armour, with a bolt pistol, then give him a scythe from a Deathshroud Bodyguard model or Typhus's scythe, and remove any Nurgle stuff from them.
Gabriel Angelos you could just about get away with a Mark 7 Power Armoured Captain model with an helmet free head, if you can find one.
But those would be a very basic starting point and not instantly recognisable unless further detailed and painted in specific ways to look like them in-game.
Good luck.