I had the numbness for a few months, but it faded away and feeling returned.
As for the difficult loop, mine was a nightmare. I had a tiny, retracted stoma. It improved over a few weeks as some swelling in my belly subsided, causing it to protrude just a tiny bit, but even that milimeter or so helped.
I managed the seal with a barrier-ring and barrier paste. Also convex wafers.
I would cut the hole in the wafer just a bit larger, and used skin-protectant wipes. My skin was difficult to manage because I have a hairy belly, which I had to shave every few days, in order to get a seal. The shaving was very difficult, because the skin was already irritated. It was kind of a vicious cycle. The skin-protectant wipes helped a lot, though. They leave behind kind of a film on the skin, which dries and creates a layer of protection.