Well I got my stuff squared away. Basically used eddy's info to calculate how many gallons, had to guess at the fill time since I couldn't accurately determine that due to the bad pump, and factored in about 2x plus a little fudge factor for pipe convolution. I wound up buying a 1/2 hp model that will be plenty adequate according to the specs on the box.

It has a piggyback style float switch, enclosed in a float bulb on the end of the electric cord, as opposed to the rod style that activates a switch internal to the pump. The good thing about these is if they go bad they are stupid easy to replace, and they can also be easily bypassed. It also has a greater, what I would call "deadband," since I can't recall a more proper term. Switches on at 15" and off at 7". With those water levels in my sump it won't cycle too often at all. I double-checked that the float isn't obstructed by anything and it's good to go.