Yes I think that you have to bluff there. And make it BIG. I mean HUGE. Like 30 or 40bb with your entire range for added pressure because you are so polarized, and you have a lot of bluffs in your range so therefore you need to bet larger.
Your value-range (54s,77,33,22,AT, A7,A3,A2, T7s,73s,32s) can all valuebet for the same overbet sizing so with such a wide over betting range you're allowed to have hands such as 84s in your bluffing range.
I would also bet larger otf and ott fwiw.

More a question of frequency i guess in theory.
So picking this combo is ok as it blocks the nuts, but also blocks 78. Unblocking the FD is not that relevant i think as i expect most players to simply cbet their BDFD.
But in my experience players hate to fold on later streets once they went to check/call-mode: esp on A-high more or less static boards. So i would be somewhat careful with this.
But once we bet, i guess trippling is kind of mandatory.

River bluff should be around 0 ev. The 4 blovks some folds like 44 and 43 but its a good blocker to represent 45 so shoving river is not a bad idea.