In your sentences, either an adjective or a verb is being modified.
I can't play football _________ enough... (verb)
This house isn't protected _________ enough... (adjective)
I'm doing _________ / I'm doing _________ in this game ... (verb)
These words must be modified using an adverb. Out of your two options, there is only one adverb: well.
I can't play football well enough to be on your team.
This house isn't protected well enough.
I'm doing well.
I'm doing well in this game.
Quick note: for the last two sentences it appears as if you can take well away from the sentence -- you cannot. Do well is an expression. You cannot say "I do in this game", nor can you say "I'm doing." You can, however, say "I do." when you get married.