Pay an electrician to bring 220V to your garage, whatever it costs. Trying to run a 2.2Kw spindle on 110V is not a good option. And you'll only get 24,000 rpm from that VFD, as the spindle needs 700Hz to reach 42,000 rpm.
And I'd get a bigger spindle. But any other spindle is likely to cost considerably more.
The pneumatics for an ATC are pretty simple. You could probably do it for ~$100. A few relays and solenoids is all you need.
I'd go with 400w-750w ac servos over the closed loop steppers. Huge performance increase, for minimal cost increase relative to the overall budget.
I'd ask a lot of questions about what the Mach4 Galil plugin supports before spending the money on it.