Re: cast offs
It doesn't sound like you would have a break with 20# mono. You likely won't see great casting performance with monofilament on a spinning reel.
You could try finding something more aero dynamic, maybe 1 once jigs with pork rind, tin lures, or a pencil popper from Gibbs lures. You only need around 1 to 1.5 ounce jigs. bigger isn't always better.
This is just me, but you might try using braided line. I like power pro, other guys don't. If you DO go with braid, you would probably want to put on about enough fluorocarbon line to make 5 or so wraps around your spool. You can join fluorocarbon to braid with a modified albright knot.
Braid line can be finicky; it's recomended that the line be saturated with water (put it in a pale) and be spooled on very tightly. Upon casting and retrieving, try to keep the line tight, and avoid reeling in loose coils of it otherwise you can get the line tangled up in the first guide (the stripper guide) and snap / break off. Braid is great for sensitivity and casting distance, but it's not perfect. Search it up on it on this site!
Another trick I wouldn't recomend is messing with the stripper guide. You could get a new size 50 fuji off the web (if you're gona stick with monofilament). Experiment by positioning it on the rod so that it tames the line coming off the spool more, and doesn't slap the rod. Just use tape at first on the guide feet. Find where you get the best distance by experimenting at a football field or something. Move the guide around and observe. Once you get it, align it carefully, wrap some heavy sewing string around the feet, and liberally super glue it on.
OK, so I rambled on . . .