I am greatly indebted to you for the help you always give me. - ok, formal
I am greatly indebted to you for all you have done for me. <-- also good, if formal.
I truly appreciate all the help you give me.
I so appreciate all the help you give me.
I truly appreciate you always helping.
Thanks awfully for always helping. - not at all formal
Thanks awfully for your help. - not at all formal
Thanks awfully for all your help. - not at all formal
I'd never use "do" with "help" as you suggested. That is "do help" - nope.
I truly appreciate all the helpful things you do. <-- ok.