I see no reason to put 20 points on a champion, with just a single wound, low initiative and one unlikely to charge. I'd take spears for the unit...
Same answer for a different reason. Most hits seem to come from impact and stomp. So I'd prefer the st6.
Don't take a champion for your Kroxigor. You risk getting into combat with something big and being issued a challenge. You three options...
I have run Elementialism a few times and I just think its fool's gold. Looks alright but never seems to deliver anything. YRMV
Not sure who "he" is that you're referring to? If you mean Dr Luke Blaxhill he played Brettonians and got 2nd overall, it's on his latest YouTube...