Whenever I have an issue with my appliance (leaks, lack of adhesion...anything!), I contact either another ostomate or the WOCNs at my wound care clinic. You say your nurse isn't much help: is this nurse a WOCN? Either way, contact a(nother?) WOCN. In my experience, not all medical personnel know everything, and some are wise enough to consult with each other to learn more about ostomy situations beyond their knowledge.
Due to skin ulcerations that presented under my appliance soon after my ileostomy, for a long time, I needed to use stoma powder with barrier wipes to help protect & heal my skin. It helped, but I found that I had issues with major leaks, too! Yes, aggravating beyond words, and I didn't know what the cause was. For me, those leaks almost became non-existent after I stopped using the stoma powder. BUT...I only found this out in a very candid conversation with one of the WOCNs at my wound care clinic.
Another thought: Try using a warmed up heating pad over your abdomen after you apply a new appliance. It can help with sealing the appliance to your abdomen. Lie under it for about 20 mins. if you can, but not on a setting so hot that it's uncomfortable. Reach under the heating pad a few times and, using your fingertips, gently press/rub over the entire flange that has adhesive on it - including immediately surrounding your stoma - that can help, too, if you are using stoma paste or a barrier ring, to really seal either of them to your skin. Then, give yourself some time before becoming really active so you don't break that seal. I know that some of us don't have a lot of time to change our appliance, but if you can manage it, you may find it helpful.
Glad you reached out, here - none of us should have to reinvent the wheel! :)