Stinks to high HAVEN (pun intended) that he's bluffing.
IF he has a 4 he might play it this way, but the big bet on the river will chase most folks out,,,,,,,thus I figure no 4
A big5 or bigT might come along as he did, and make a big river bluff knowing he's putting the screws to you but his sizing is terrible for value purposes, but does give him outs if you decide to call with mid pair or a smaller 5 or T.
So my logic says we only worry about TT, QQ, KK, AA hands and in each of these cases, Its hard to believe (not really that hard a 2nl) that villain holds till the end for the big non value raise.
Other considerations is at 2nl, anything can and does happen, as posted the only read we have on villain is his stack size. This is a shame, any read would be helpful in determining which part of the general population this villain fit into.
I call his bluff here. Knowing full well I could be dead wrong, but liking my logic process thru and thru.