Everything you're feeling is so normal ChiMama so be at peace that you are going to make this and it will be easier than the colon surgery. As far as lung capacity exercise I would do fast walking for a good 5 minutes until I was breathless then do slower walking for about 10 minutes and then back to the fast walking. It really helped me along with the spirometer, which I used 3-4 times an hour and I'd set my goals to get that darned thing right to the top...but you set a goal that will challenge you and help you improve your capacity.
It sounds like you're doing a lot of good things for yourself so please continue with them. You'll be happy later that you did.