"〇〇だったば、...." is this legitimate?
I want to say "If it was 〇〇, then... ", is "〇〇だったば、..." the right clause?
I'd use だったら
No. I would use だったなら if you want to use a past tense conditional. だったば doesn't appear to be standard Japanese. Looking into it, the phrase だってばよ was popularized by Naruto, and is a slang version of だってよ (I heard that, it seems that).