Yes, EU2 is an abysmally frustrating MP experience much of the time. Too oft, are the times I can count myself getting shortchanged by superficial player changes and subs. It is indeed the time lost that usually hurts the most. But take it in perspective, if you can stomach losing wars and suffering 'unfair' setbacks you are halfway to being twice the player most are.
Recovery and endurance are the bedmate skills of Diplomacy. Take this as the RP'd terror of unpredictability in real world affairs, of madmen reaching the throne

.
To lose a reliable player at this point though, would be a blow. We are consistently struggling as it is, nor is your war (materially) that terrible. You lost 2 provinces you took earlier (no net loss), and made Austria inflate more then 2x as much as France. Temu, on the other hand has been truly hardpressed but I get the feeling he intends to stick around ... make it past 1800 Fraese, win or lose it will feel better.