If you really know so much about HPV you would know he's not turning into a tree. He just looks like he is... >>
Of course he ain't gonna suddenly gain the ability to produce chlorophyll/chloroplasts, just like his cells aren't gonna become plantlike at a molecular level.
I already mentioned the clothes. He's a big bigger at the ends of his feet and all, but he still looks like he could get the clothing over it. Like a plaster cast or something. You can still get the clothing over it, sometimes even with just minimal annoyance...
Besides, no bone in that tissue. I highly doubt it'll be that inflexible... >>

Just my opinion on the last bit...