Frenzy is definitely something that could use some clarification. By the book, the only real benefit of frenzy is ignoring wound penalties. It seems to be a common belief, probably backed up by rules somewhere in Laws of the Night or something (Tom? Conor?) that being in frenzy also renders you immune to many methods of mind-manipulation (Presence, etc.).
There is no frenzy retest. I get what it was for and don't necessarily disagree with its existence, but it's never been anywhere in our house rules or any rulebook that I know of. Similarly, being forced to dump all your Rage is a reasonable thing but not actually written as a rule anywhere that I'm aware of. Getting one Rage per round is right out - there's a Gift for that. I am not denying that any of these things may have happened previously, I'm just saying that as things currently stand there is no basis for them in the rules that I'm aware of. Maybe we want to change that! We can talk about that.
As for using retests in frenzy, that's a good question. As per Laws of the Wild pg. 185, "The character can bite, claw or run, and that's all. The character can spend for extra actions but cannot engage in complex actions, use Gifts, step sideways, and so on." This bit actually seems to strongly imply that frenzying characters DON'T need to dump all their Rage ("can spend for extra actions" not "must spend for extra actions") and, in my opinion, disqualifies getting a bonus from Martial Arts. I think Brawl is a reasonable retest, and because of our rules about having Martial Arts and Brawl (i.e., you can't) Martial Arts is also therefore a reasonable retest, but being a karate master does not get you a bonus trait on ripping someone's guts out with your claws in frenzy. Soaking with Survival certainly seems reasonable since it's purely reflexive, Dodging is less clear. I think a case could be made either way for Dodge.
I think it's reasonable not to be required to spend Rage when your character is attacking an ally, and to not have to spend Willpower to refresh if you don't want to (punching yourself into exhaustion is a thing). I think it's unreasonable to choose to bid one Trait when attacking an ally; this implies a level of restraint that frenzy really doesn't allow for by its very nature. If you can use retests while frenzying, using retests against allies falls in the middle here, in my opinion.