Welcome to the forum, Joelam1te.
Your stats are above average in length, and your girth is downright large. Congrats on that.
I don’t see any reason that you’d lose any girth. Our penises are not really like taffy. :)
Don’t spend much time worrying about your wife’s ex. First of all, she’s with you,not him. Secondly, it’s highly improbable that he was anywhere near as large as she described. Women are notoriously inaccurate at measuring or estimating sizes.
Proceed carefully with the Newbie Routine and good luck. With your startIng size, you can only end up really large!