Is 99 bananas a suitable liqueur for bananas foster?

I agree the artificial taste of banana in liqueur can really come out after cooking it down or flaming it. I would stay with just the rum.

Bananas foster is typically made with rum instead of liqueur. What you have will work but may be sweeter than the classic with a stronger banana taste.

Yes, should work just fine, although you can also make bananas foster with just rum. Any banana liqueur is going to add a slightly fake or exaggerated banana flavor.