I've never donated much and now my thinking is I'll take some if I can.
I'm with ya. I probably put in somewhere around $1-2K, which i suspect is on the low side considering my employment and how long I've been in. I'd love to have it back, but I always prefered to donate cash because even while I was in I didn't like the possibility that someone might be tracking my donations. That being the case, there's no way to request it back.
Also, I suspect that if you tried to give a donation with a bunch of contingencies like those specified, the WTS would probably say "no thanks" hoping you'd just give it to them anyway, like a good JW. If they did take it, you can bet they'd fight giving a refund. If i remember correctly there have been a few cases documented on here where people gave money on contingency that they could get it back if needed but got a fight when they wanted it back (or got heavy pressure to convert it to an outright donation)
In any event, I've taken to getting my money back by trashing 30-40 magazines every month, depending on how many meetings I make it to. I wonder how long it will take for them to recognize a disparity between magazines ordered and placements reported.