Basically, if you want to know something related to the comic, ask here. Then we'll give you an answer or a reason for there not being an answer.

What was it that happened to Muffinman when he first discovered his powers? And how far has he gone to test just how impervious he really is?

We're planning on revealing Muffinman's origins some time later in the story, so I won't say anything about that now.

But as for your other question, I would assume he just throws himself into whatever challenges comes up, assuming he'll be alright in the end. The observant reader may have noticed that Muffinman doesn't exactly have great presence of mind, but he sure is persistent.

I don't know if I qualify as an observant reader buy I did notice that about him.