Hi Alc
First 2 are fine.
I'm late on my/the payments is fine, but, if given a choice, I'd use 'I'm behind with my/the payments'. This is the more commonly used phrasing.
4 fine
Don't tighten the bolt too much.
All the rest are fine till the last.
Apart from/other than needing me to sign the contract, what other thing (or, what else) is