Those engine mount area stress cracks are semi-common with K0 frames. Why some frames develop these, while others <ostensibly> never do, is a question I don't expect to be answered, definitively. I suspect it's a result of structural improvements (Honda implemented running changes with the frames) and loose engine mounts. The engine is a critical part of the structure...similar to the axle assemblies and swingarm pivot assembly. Loose axles, swingarm pivot bolts and engine mounts are disasters waiting to happen (and thus preventable). I usually add metal when doing this repair...it's probably overkill. One thing I would strongly suggest is carefully inspecting the rest of the triangle area... they usually form cracks on both sides...after the bead blasting. 90% of the time, there will be tiny breaks on the opposite side that only become visible once the surface is clean & uniformly colored. FYI, you caught this at an early stage. Left alone, the cracks not only spread but they first "V", then develop a dendrite (think tree roots) pattern, just like seat pan breakage.
The seat latch mount area, well, we know the cause...using the seat as a lift handle. That's an easy repair. Knock down the metal, just enough to give you a slight (few thousandths of an inch) extra depth for welding, from the top. Once the welds have been dressed, the seat latch hides the surgical scars. And, this also minimizes the amount of finishing work needed on the visible side, in the wheel arch.
It doesn't look like much deflection, in this pic. As long as you can apply the force, needed to straighten the mount, to the short section inboard of shoulder, I think you'll be okay. The shoulder, being a sharp 90-degree transition, is a stress riser. That's where my shock mount snapped-off.
The most common issue I've encountered with bent shock mounts is that the bend extends to the central portion...inside the frame. That alters frame geometry in ways that cause a number of concerns. Chief among them are the pinched-in frame walls and angled seat supports/shock mounts themselves.