This is a HU SNG. I had only played him for 18 hands. This was his 1st 3 bet. I had been stealing close to 100%. I understand that its an obvious 4 bet shove with 66 if he is 3 betting a lot, but is it still good to shove in 50 or 60 big blinds vs his 1st 3 bet?

yes

4 bet 22+, AJo+? call KQ? fold everything else?

dunno about the fold everything else part, lol, I like to call a lot of stuff to 3bets this deep, but without reads its ok to ship 22+, AJ+ yes, maybe I'll flat AJ more than shove and some times I'll shove KQs too. I'll also call 22-77 some, and maybe 88-99 too sometimes.

you say its ok to ship 22+, AJ+ without reads but is him only 3 betting once in 18 hands a read(5% 3 bet) which would indicate that I should be calling/shoving a tighter range/folding out some weak pairs and hands like A10, AJ, QK?

If you say sample size isnt great enough, what if it was a larger sample size?

18 hands is nothing, but yeah I wouldn't shove AJ and probably ship 88+ (maybe 77), and just call 22-66/77 and AJ

if it's a larger sample you should be able to tell what his range is and act accordingly, if you can't tell yet act on the "unknown" basis

also his results matters a lot, and betsize too, by this HH I can't tell exactly if he made it 180 or 160 (or if you made it 60 or 50), but if you made it 60 then the 160 size is much more "bluffy" and I'll be shoving wider, and on the results if he is a reg I am shoving all pairs and AT+ (being SUPER HAPPY about it if he made it 160), and if he's a fish I dunno, you should probably be able to tell if he is a nittty fish or a splashy fish and call more vs the nit and shove wider vs the crazier ones