I've been donating every 8 weeks and have come to realize that it's actually too much for me. My hemoglobin keeps dropping EVERY time and my blood pressure is always lower lol. I'm going to hold off to once every 12 weeks and assess from there :).
Stretching before is bad, but a few mobility drills without forced stretching can help for some. Definitely stretch afterwards if you're going to incorporate some form of static or forced stretching.
I personally feel cardio either first the in the morning while fasted or post workout would be best. Some studies show cardio to have a greater fat burning effect when you're depleted of glycogen.
You'll know whether or not your body can handle it. I've done 3 cc's in my delt before and it held up pretty well. Some people will have a bit of "leakage" but I didn't seem to have an issue. I would consider working quads into the rotation if pinning glutes becomes too much.
My guess is it's already in and out of your system so fast that you don't have any sides at that point. Were your workouts later in the day when you had night sweats initially?