Yeah new engines are a pain to start until you get them broken in. The roto start is certainly worth it, even if you just get the back plate and drill wand, you can use a drill to start it.

I ripped through the gears on my starter box twice while trying to break in one of my truggies. I found out it it is much easier to start a new engine if you take a heat gun and heat the engine to 150F before you start it. A hair dryer will also work and is probably safer.

The other trick is to put a second washer on the glow plug to help reduce compression or loosen the glow plug 1/4 - 1/2 turn. 

Also, make sure the piston is in the down position before trying to start it. Take the glow plug out and move the flywheel until the piston hits dead bottom. Mark a spot on the flywheel with a marker or paint pen so you know when the piston is at dead bottom.

Take the glow plug out an make sure it lights up with your glow starter. I've gone through several plugs while breaking the engine in, it's really hard on the plugs.

Also, you had mentioned you had the HSN set at 4 1/2 turns. Start it at 2 1/2 turns. There's a misprint in the manual. It's probably flooding because it is too rich.

Make sure you have the idle screw set so the carb is open 1mm at idle. You'll have to adjust this as well when the engine breaks in.