Sunny has 212K and I'd driver her just about anywhere. You won't hurt your Miata by driving it! I probably drive as hard as anyone on the track ( ), as far away as Indy, Cleveland, and Poconos for track events, and always driven home. Besides, there is always someone who would help you out if you got stranded.
As for towing weights, we towed two SM's with too many spares, tools, scales, alignment plates, four extra sets of tires, fuel, etc. to Hallett last July 4th in the motorhome, and weighed it in OKC and the trailer axles were right at 12,000 pounds.........OUCH! Before this rig, I could tow Speedie behind my V6 Dakota, as long as I didn't have to stop! SM 2200#, trailer 1600# with a set of tires and tool box, truck 3200# I only made short trips that way, longest to TWS.