Hi,
OK! I'll make you a deal. You stop analyzing me and my boat. I'll try my best to reform you and your thieving ways.
I wonder if "your thieving ways" in the above can be replaced by "your theft/thefty/stealing ways?" If not, why not?
'Theft ways' is not idiomatic. 'The adjective form 'thieving ways' is better, and more idiomatic. 'Thefty' is not a word.'Stealing ways' is not idiomatic.
This obviously needs a suitable context.
'To reform you' seems a little bit formal to me when used along with a colloquial term like 'I'll make you a deal'.
Best wishes, Clive