Depending on how bad that pawl is worn, you could either dress it up with a file, along with the notches it drops in, or build it up with weld, and dress it with a grinder, or file. This is where a 110V mig comes in handy..!! Or, I did find one place online that still sells new ones, since Case/IH apparently doesn't, or it's a special order item. Here is the link to the aftermarket ones...
OEM Tractor Parts WEB Catalog 2012 - 2nd Edition (2) Page 79
The one pictured looks awfully round on the front to me. Both of mine have a little flat spot on the lower front rounded part, to drop, & lock neatly in the notch. Even at that, I don't trust mine on much of a hill, I'll turn the front wheels, usually full right if I need to leave it running on a hill. I bought a BN about 25 years ago that ran away, from the pawl releasing. Broke it in 4 pieces... Still worth salvaging a few things from it.
On the starting part, it sounds more like an electrical problem to me. If it's an older battery, it could be getting tired, and not taking a full charge. Or, the generator, or voltage regulator aren't putting out enough to keep up when starting & stopping frequently.
Not sure what size your battery cables are, but they should be no less than 1/0 cable. If they are automotive type 4 ga., it will seem like the starter is lazy, and do that. Some tractor dealers will make custom battery cables, and also will some NAPA stores. My local NAPA did not have 1/0 cable, but did have 2/0. I went ahead, and had them make me a set for Dad's old Super C. Cost was right at $80, but starts like a new tractor, even down around 0º.