Nuttish

The photo above is the correct tool. It's called a hook spanner. You might be able to remove the fastener by lightly tapping a large standard screwdriver or a drift against the inside face of one of the slots. Too much force will damage the bearings and potentially the shaft. Make sure to inspect the end of the shaft to determine which direction tightens the fastener. It's not entirely uncommon for drive components to be reverse threaded.

Those RM Leather Supply mesh cage rollers are a game changer. The knurled brass ones can leave marks. The mesh ones work great with whatever consistency of edge treatment you use.

In my limited experience, cheap stones are just fine if they're (a) flat, (b) the correct grit, and (c) used properly. One cheap Japanese combination water stone with one side at 600 to 1000 grit and the other other 4000 to 8000 grit and one courser combination oil or water stone will serve you well for a long time. I've been using the same King KW-65 and Norton course/fine bench stone for years. Just be aware that the water stones will wear much more quickly than the oil stones, though they're also much easier to bring back to usable condition. Just stick a sheet of 150 grit paper to a piece of glass or acrylic and dress the surface until the old tool marks are removed uniformly. Depending on the oil stone, you can dress them with progressively finer files - obviously only do this with a dull file you no longer intend to use on metal. Sometimes the surfaces of courser stones are difficult to use because they're so crudded up with oil/metal, so you can sometimes bring them back by soaking them in degreaser and pressure washing them. Don't pressure wash Japanese style water stones - the manmade ones are basically just fancy clay.

Owosso Graphic Arts in Owosso Michigan

Make a solution and apply it with a graffiti drip pen.

The foot is considered a wear part. The old manuals say you can send them in to be reground. I doubt anyone does this anymore and new ones cost enough that a bit of my own time is worth it. I've dressed feet by sticking progressively finer sandpaper to the outside of the bell knife with double sided tape to match the radius of the right edge to the radius of the knife. Then used sandpaper wrapped around a dowel to dress the inside taper leading down to the righthand edge and round the righthand edge over so it doesn't mark my leather.

If you have Illustrator or Inkscape, you should consider drawing your mark in vectors and having some magnesium or copper plates made from a place like Owosso Plates in Michigan. They make letterpress and hot stamping dies by the square inch. Just figure out what dies you want and what size sheet they'll fit on. If you're hand stamping with a mallet, you can JB Weld them to a piece of steel rod that adequately supports the entire back of the image area of the die. This will be many times cheaper than having a single custom stamp made and you'll be able to get a variety of stamps.

The top results of my first Google search for "pfaff 1245 feet" contained listings for good used OEM Pfaff feet for your machine costing less than $50. The Chinese feet from kwokhing.com meet your description of not fitting. Half of the feet I've gotten required some amount of filing or drilling to work. Something to keep in mind when looking for used parts is that they're often sold by part number, not the machine or machines they fit. For the most part, all Pfaff parts are stamped with a part number. Get the 1245 parts book for a list of all feet, plates, and accessories for your machine. There are loads of used parts out there.

There used to be a hackerspace in Barrie and IIRC folks were working on founding another downtown. They'll pretty much always have laser engravers suitable for cutting the 1/8" acrylic you'd use for templates and I'm dead certain you could find a nerd willing to cut your pieces for way less than a job shop would charge.

This is the definitive encyclopedia of knots. Maybe you'll find something interesting that suits your purpose. https://archive.org/details/TheAshleyBookOfKnots

Find a "surface plate" intended for a machine shop or a piece of marble or granite from a grave monument fabricator.

I wouldn't say these things are particularly easy to repair at all if there's appreciable runout in the sharpening stone or bell knife drive shafts. If the thing is running, color the knife edge with a marker and lightly touch the sharpening stone to the edge and see whether it contacts relatively evenly. If not, I'd pass unless it's cheap and you already know how to fix these things or want to learn how and like spending money on parts. Reiterate what others said about the accessories.

The Fortuna machine is the industry standard. I would expect the Cowboy clone to be good quality. Parts are going to be easy to get from them or Campbell Randall. That's the machine to lean toward. There really aren't any alternatives to that type of skiving machine anyway.

Rubber cement some wide rubber bands to the bottom. Or just paint the bottom with a generous coat of rubber cement all on its own.

What kind of leather is that, what tools and chemicals did you use, and what's wrong with your edges in your view?