I have a 150 in my M5 which is listed for 170-190 and it's fine. I just shortened the closing loop. You could probably get away with it as long as the canopy you put in there isn't a 7 cell or low pack volume 9 cell
http://www.usairnet.com/cgi-bin/launch/code.cgi
I use this in conjunction with weather underground to get a pretty decent idea of what the weather is going to be. It's still only good that day or sometimes the day before
I jumped about 9 months ago with a cold and I'm still having ear issues from it. I would say stay on the ground until all the symptoms are gone. There will always be more jumps and long term ear problems just aren't worth it
I had the same problem when I first started using my N3 as well. It turns out I wasn't pushing it into the cutout in the foam. Once I did that I couldn't even feel that it was there.
Do yourself a favor and spend much more than an hour or two in the tunnel. The amount of progress you'll make in the tunnel with several hours will vastly exceed the progress you would make with a few hundred skydives and minimal tunnel time.