Hey Dnl83,
Welcome to the irrigation boards.
Sounds like you have several things going on all at once that could be complicating matters.
Learning to irrigate is very much like a marathon, not a sprint. It may take you a while to figure out a routine that works best for you. Keep in mind, we are all different in our irrigating experiences.
To answer your questions:
1.) You may be getting what we call "late returns" because you are not getting your colon completely empty. For me, one infusion is not sufficient to get a good "cleaning". For me, the best routine is multiple infusions. I infuse 1500cc. Wait on returns. I infuse another 1500cc which help to get output that was hiding in corners and such

I then infuse a 3rd 1500cc as my "mop up" infusion. This ensures, for me, a day without output. When I initially started irrigating, I only did one infusion of 500cc and got those later returns later in the day. I had to work out a routine that seemed to work best for me. I would suggest adding another infusion after your first returns are complete, and see if that makes a difference for you.
2.) Your colon is constantly producing mucous to aid in the movement of output. Sometimes, if the water is too warm, it may produce more in order to help protect/heal any irritations. Sounds like you may be having mucous combined with more liquid output after your initial infusion. You may find that the second infusion will clean you out more completley, which will likely decrease this kind of output. I simply call is "spooge" for lack of a better term!
3.) With the pain meds you are taking, your colon is likely spending a lot of time in a resting state (limited peristalsis). When this happens, you stoma will "expand", or seem larger. During peristalsis, your stoma will contract, and appear smaller and tighter. It will cycle between rest and peristalsis. I think you would have had to get really rough with the stoma in order to injure it with irrigation. The pain could be a number of things, from nerve endings, to scar tissue, etc.
Try to establish a consistent routine. Same time of day, same amount of water infused, same temperature of water used, etc. Try that for a week and record your results. If you''re not getting what you want, change it up, and repeat for another week, keeping a consistent routine.
As you noted, you have a lot of other things at play here, that may have an effect on your success, such as pain meds, possible scar tissue, meds to decrease impact of pain meds, etc.....
Hope I gave you a useful tip somewhere in there. Others will be along to share their experiences. We like new "gatelets"!
David