Pre is spew on his part, especially vs a 2.5x. 49o is way too weak of a hand to defend and plays terribly postflop. Flop seems fine, you can also call and let him shove turns with his bluffs.
Smaller sizing pre for what? It's not hero's job to minimise opponents mistakes. If it's the kind of table where folk/the bb are flatting 94o then let them do so at greater cost.
ye 2.5x is competly fine. i would go a lil bit smaller otf but im okay with 800. i call flop and call most turns beside 9 pbb, also if he x raises with J7dd or smt like that we reaaally dont want to fold out that hand with a raise otf, so keeping a few more probable bluffs in his range ott is pretty mandatory imo