The translation you have is grammatically correct though I'd remove the comma. However, indomitus means "untamed" or "ungoverned", so I think R. Seltza's interritus is a better word choice. His translations are correct as well.Usque ad mortem in aeternum, indomitus
Both sentences are active. They just put the prepositional phrase in a different place.active
To avoid two prepositional phrases in a row, I might be tempted to replace in aeternum to an adverb like sempiterno or perpetuo, though I guess it isn't really wrong to keep the prepositional phrase.The translation you have is grammatically correct though I'd remove the comma. However, indomitus means "untamed" or "ungoverned", so I think R. Seltza's interritus is a better word choice.
Correct but a bit overcapitalized, in my opinion.His translations are correct as well.