Sharpening is easy. ( with the right kit and technique)!
We cover that in the first two days of the tool tuning course before getting on to Plane tuning / rebuilding / fettling and precision planing which is the fun part.
I am having trouble understanding what you mean by "the clamp across the front slab"? Are you referring to the vise, or is there another picture that better shows what you are describing?
If you have, or can get from your local library, my book 1, there is a photo on page 12, top centre.
If not here goes;
Suppose you need to plane the edge of a wide board or table top.
One end is held in the vice and the other is flapping about in the breeze. The loose end is clamped to the front edge of the top slab, with a short sash clamp resting on top or under the surface of the slab. The far end of the clamp is acting on the back edge of the main slab/ bench top.
The under the bench top option is only possible if the tool well is removable and of some width.
This may be clear as mud, but best I can do at this time of night.
>I have ground a number of blunt saw taper (triangular) files into dovetail chisels, especially skew chisels - and the corners become razor sharp. Running the edges lightly along the grinder avoids the blood - they do not need to be anything like that sharp. These are super efffective for cleaning out corners, the steel in old chisels is excellent, pretty hard and cost = zero.
Large 3 square chisels are probably even better, but I have not worn them out sufficiently yet, and they did cost $3 new.
>When planing the edge of a board that is fastened in a vise at the left end, the plane is held somewhat in front of your right hip, which is right next to the bench or the side of the board. You finish planing just as your hip approaches the vise. If the vise is at the right end and the board extends to the left from the vise, you have to keep your body out further to avoid bumping into the vise. It is not impossible, just a little bit clumsy because your body is off to the side instead of in back.
If it were my bench I think I would turn the top around, putting the mistake in the back, or just inlay a patch in the mistake.
>I'll do a dry run to try it before fitting the top any further, to see if this is enough of a problem to justify fixing it properly. As it's for my father, who isn't going to do large amounts of stock prep or similar work, I suspect he won't be greatly inconvenienced. The fact that the top is now flat and has accurately square ends he can clamp things to is probably a big enough improvement over my original effort (28 years ago!) that he will find it more useful even with this oops.
When I make v2, which will be for me and on which I would like to do as much as I can, your point is one I'll be bearing in mind!