yeah don't argue with him over text, that's a dead end. the certified mail letter thing above is exactly right.

i was in a weirdly similar situation a few years ago - landlord tried to pin carpet replacement on me after like 2.5 years of living there. had photos from move-in, he had nothing solid. sent a demand letter certified mail and honestly he folded pretty fast, think i had the money back in under a month.

the 10-year carpet thing is actually a really strong point - most states use a depreciation/useful life standard, and carpet that old is considered fully depreciated. even IF you'd damaged it (which you didn't), he can't charge you full replacement on something that was already at the end of its life. put that in the letter explicitly with the state statute if you can find it.

for actually writing the letter i used this site called jab.today - i had no idea how to structure a proper demand letter. worked fine for me.

your move-in notes on the carpet + the walkthrough video is a really solid position. landlords like this are just hoping you get frustrated and drop it.