Hi Dave,
Glad to see you're getting your head around a compromise you can live with - a hunt should be about the experience, not gritting your teeth monitoring a budget.
In case it's helpful, I just looked at the cost of an Uber van from Joburg to Thabazimbi - you'd be looking at R4000 ($280) one-way. Of course you would spread that amongst your party. So that gives you the ballpark of transport costs if you decide to DIY. Renting a car is an option too but I suspect that a big enough vehicle for 4 may pushing $100/day, so not much cost saving plus the hassle of navigating.
I wholeheartedly support the idea of abandoning the trophy/import concept. I'd say you're better off shooting an extra animal or 3 on your 1st hunt with the money you save. Unless the hunt totally blows up, I predict you'll be back in future and have a firmer idea of what animals/trophies you want and can take a longer run-up in getting your budget figured out then. And if you want trophies then, you have justification to shoot springbok etc again!
You probably appreciate this already but your day rate covers meals, service (cooks, cleaners, trackers, PH, usage of vehicles etc) which are fixed costs whether you hunt or not. To expect the PH to take you out varminting for jackal etc gratis for more than a day may not be met with much enthusiasm. You may have more joy negotiating cheaper rates for surplus/additional animals once you're on the ground. Not every outfitter/PH will do this but many will if there's lots of time left after filling your quota and they see that you are a serious hunter. Of course, if they think you're free-loading then the opposite applies.
Good luck and I hope you find peace and ultimately excitement with your plans!