how much monounsaturated and polyunsaturated fat is TOO much

The total fat on U.S. food labels includes the unsaturated fat; they just don't always break them out. So, assuming you're using accurate MFP database entries, the total fat in your food diary already includes the unsaturated fats. Subtract saturated fat (which is supposed to be included on the food label in the U.S.) from the total fat, and you'll know how much unsaturated fat you're getting. I never heard of dietary advice that set a separate limit for unsaturated fat, just for total fat and saturated fat. If you're getting enough unsaturated fat that you're going over whatever total fat goal you've set for yourself, then I guess you're getting "too much of the good stuff."

Personally, I don't really worry about limiting total fat; I just try to avoid added trans fat and to keep my saturated fat in the neighborhood at or below a third of my total fat. And I've lost 40+ lbs, and maintained my initial 30-pound loss for more than a year (while slowly losing another 10+ lbs), so clearly it's not impeding my weight loss.