Re: Are the highligted words being used correctly in the sentences?
For the situation in 3 & 4, I would say "Did you help me by asking your friend if I could join them?" as I said before.
"Did you help me ask ..." means "Did you come with me when I asked something and did you help me while I was asking it?" I can't imagine a situation where that would be necessary.
If I were in a foreign country and I didn't speak the language, I might say to a native speaker "Would/Could/Can you help me ask at the bank about opening an account?" I would be asking for the native speaker's assistance. Afterwards, I might say "Thank you for helping me ask at the bank" but it would be pointless for me to say "Did you help me ask at the bank?" because I would already know the answer. Either the native speaker came with me and helped or he/she didn't.
Remember - correct capitalisation, punctuation and spacing make posts much easier to read.