Challenge #19 - The Family Man // Help!

So I've attempted this one around a dozen times now and I'm really struggling. I've reached Isaac four times but no matter how strong I have been prior to it I can never seem to beat him. I've been running into the Bible a few times which helps with the Mom bosses, but I've only encountered Box of Friends once and it was in a shop that I didn't have enough money for.

Should I just keep trying in the hopes of getting OP or is there some kind of strategy that I'm missing out on, especially in terms of beating Isaac?