Great list! I would love to try this!
For your questions:
Everwinter's Master isn't great, honestly. Considering that you want to keep your FLoTT alive for as long as possible, Massive Bulk may be better.
All BCR will struggle against magic. Taking a Fungoid or two might help, but not a whole lot. This is one of the pitfalls of playing BCR, so yes, you may be weak against magic, but any list that you make will be.
Your list's melee strength is very middle-of-the-road. Most Rend (not all, but a decent chunk of it) comes from melee attacks. Ethereal Amulet is great on a FLoSH, which is used in melee, but not necessary on a FLoTT, which still stays back to snipe. MWs also frequently come from melee, so Ignax's scales isn't the way to go. The Pelt of Charngar would provide healing on top of what was already being done by the Huskards, so I think that that would be a good choice.
As for the list itself, I think it's FANTASTIC! I've seen many a BCR list implement the Frost Sabre or the 3-Thundertusk strategy, but never combined nor done this well. Awesome!