Answer 1

I'd recommend not having the starting point on the sloped dustblocks.  In the editor you get instant control, but playing the actual map you fall a bit during the start countdown so the first slope is already destroyed.

Answer 2

I realized this after publishing, I hadn't thought about it beforehand. I suppose in the future I should manually move my maps to the custom level folder and test them there before publishing, to see if there are any discrepancies between the in-editor test and actually playing the level.

Answer 3

The only difference from playing it in the editor is that there's a 1-2 second window when playing the level where you can't control your character at the start of the level.  It's only an issue if you're starting in the air or on dustblocks.

Answer 4

Or you can just hit replay, even if you are in editor it will give you a countdown just like a published level.