His donk should consist a lot of air in order to consider it. VPIP is important but watch his actions as well and the board. From my experience such a donks wont fold to a raise most of the time.
So just fold if you are not convinced to raise. Call is worst option. Anyway I saw too many players like him to not see their donking range is all over the place. Sure I dont know this exact player but I know how players with similar profile plays, so I raise. Even if I get call then its still ok given how many backdoors we have with JT in spades. Also you shouldn't always assume that you will never fire bluff on turn - fish as you said may bet/call bottom pair there, but how often you saw sticky fish calling it down with that weak hand in big pot?