1) It should hit the post, but it shouldn't go towards the drain, it should hit the post a hair farther to the left, so it bounces to the right of the middle. Check alignment of the mini-flipper, when I had that aligned wrong, it would graze the post and go SDTM. It'll usually go SDTM if it misses the post entirely as well (achievable via incorrect alignment of upper mini-flipper)
2) The pop bumpers are a mess on TZ. I think Pat Lawlor admitted that that wasn't his best work at some point. Randomly adjusting pop-bumper related things (the kind of rubbers, sensitivity of bumpers, etc) might help this. But you really just want to keep the ball out of the bumpers at all costs when playing TZ.
3) Yeah, lots of airballs. The one next to the slot machine is terrible - I took extreme measures with that - I replaced the backing on the "reinforced" target with a quarter inch thick steel bar. Works great, that target doesn't generate airballs anymore.