Exclusive pumpers I have some questions

sdo_082989

I am starting to exclusively pump due to some problems with DD latching and nursing for 6 or more hours everyday. I have pumped since I was in the hospital to get my milk to come in faster and then I pumped for a little bit after feedings to build a freezer stash. Anyway to the point...right now I pump every 3-4 hours, pump each side for 30 minutes and get about 3 ounces per side. My questions...

Is this ok? Will waiting 3-4 hours before pumping decrease my supply? Should I up it to every 2 hours? 

Will my supply most likely stay pretty close to this or will it eventually drop?

Is pumping for 30 minutes not long enough or too long for each side?

What pump do you recommend for EPing? I just have the EvenFlo SimplyGo electric right now and I know I will need something better for EPing.

Any other info or tips would be GREATLY APPRECIATED.  

Edited to add: Stupid question but what should your nipples look like when pulled out of the pump? Mine are pretty big when I am done pumping. Is that normal?