I'd say his 3-bet calling range is something like AQ+ and TT+. I have no clue what you have but his range is incredibly strong seeing that hes a nit and he called your 3-bet from UTG where his PF range will be the strongest.
agree he might be calling a tad lighter like AJ cause he has to know im 3beting him a fair amount
tbh when he bet that amount i was kinda happy because i didn't think he would bet that amount with hands he was super happy with almost like hes trying to fake it.