My opinion, if you want a bobbed hammer make the gun DAO. If you want to retain single-action operation, keep the spur for safety reasons. A good gunsmith can either bob the hammer and convert it to DAO, or "soften" the sharp edges on the spur for carry if you want to keep the SA option.

Again, my opinion, but I consider chamber chamfering good to have, but not necessary. It makes reloading smoother, but reloading is almost never done in the middle of a self defense encounter, and on the rare occasion it does happen it almost never has an impact on the outcome. I practice reloading with my 642, which doesn't have chamfered chambers, but it's a lower priority to me than being able to draw quickly and smoothly. I don't expect to need to reload in a gunfight, but in the unlikely event I have to shoot in self defense I don't want to wait for the police with an empty gun.

If you do get the chambers chamfered, don't chamfer the extractor, as that could potentially cause it to slip off the case rim, causing the case to get stuck under the extractor star. Fixable without too much difficulty, but it's something that's best to avoid in the first place.

I remember seeing a hand tool for chamfering chamber mouths being offered by Brownells, so that may be worth looking into.

As I mentioned in my previous post, I don't care for most of the grips available for the SP101 (they almost all seem to have really deep finger grooves, which I don't like). Eagle Secret Service grips are available for the SP101, which seems to me to be the best option (shallow finger grooves = tolerable). They're based on the Spegel boot grip, which is what the S&W OEM boot grip is based on. They might be worth looking into. I have a set of the Secret Service grips for one of my 642s. I like them, but they interfere with my speedloaders so I replaced them with something else. I don't know if that's a problem with the SP101 version, but you said you load single rounds so that probably won't be an issue. Also, I've never handled the SP101 version, so I can't comment on any differences between it and the J-frame version.