Look I like it too OP - with the proper Welsh pronunciation (Mal, short a). But any non-Welsh in seeing it written down would pronounce it Mould-win (or like Baldwin), and that’s just awful!
You live in Wales, so you’re probably safe on the pronunciation day to day, but then unfortunately you’re also open to the “old hill farmer” stereotype.
Those completely unfamiliar with the name will say it wrong & think it’s horrible.
Those who know the name may be prejudiced because it’s “old man” & therefore think it’s horrible.
If you like it, use it! Mal is a great short version for all purposes anyway.