Against a standard player's MP open I think I'd be going as far as 55+ with the rejam here.
Villain seemed quite nitty on the HUD, making this shove semi bad?

PokerStars - 300/600 Ante 70 NL - Holdem - 9 players
Hand converted by PokerTracker 4

BTN: 35,017 (VPIP: 60.00, PFR: 20.00, 3Bet Preflop: 0.00, Hands: 10)
Hero (SB): 10,781
BB: 9,880 (VPIP: 0.00, PFR: 0.00, 3Bet Preflop: -, Hands: 2)
UTG: 18,119 (VPIP: 22.22, PFR: 14.29, 3Bet Preflop: 4.55, Hands: 64)
UTG+1: 9,880 (VPIP: 0.00, PFR: 0.00, 3Bet Preflop: -, Hands: 2)
MP: 9,880 (VPIP: 0.00, PFR: 0.00, 3Bet Preflop: -, Hands: 2)
MP+1: 31,921 (VPIP: 15.58, PFR: 6.58, 3Bet Preflop: 0.00, Hands: 78)
MP+2: 10,000 (VPIP: 18.06, PFR: 9.72, 3Bet Preflop: 5.26, Hands: 73)
CO: 31,920 (VPIP: 20.93, PFR: 10.47, 3Bet Preflop: 5.41, Hands: 87)

9 players post ante of 70, Hero posts SB 300, BB posts BB 600

Pre Flop: (pot: 1,530) Hero has 8 8

fold, fold, fold, MP+1 raises to 1,500, fold, fold, BTN calls 1,500, Hero raises to 10,711 and is all-in, fold, MP+1 calls 9,211, BTN raises to 34,947 and is all-in, fold

Flop: (33,363, 2 players) 7 9 J

Turn: (33,363, 2 players) 7

River: (33,363, 2 players) 7

You can't call
You can't fold

Only move is 3b squeeze, only sizing with 18bb is ALL IN

Super super standard spot

Yes we don't have enough hands to say that MP+1 is really a nit and we have reasonable equity against calling range - even better if he is capable of calling your shove and then folding to the overshove..

If there are no ICM considerations, then 88+ AQ+ is the range here for 18bb regardless if villain is nitty or not. Even if 88 is close, 99 would be 100%.
As bencb789 says, if you are one hand away from correct shoving range, you are doing well.

I fold often 88 and 99 if its against UTG or UTG1.