I agree with FJ12. The fan coming on is not a problem. Mine comes on regularly in traffic in 35 deg C heat and can stay on for a while when stopped at lights. I find the fan comes on when the gauge goes up by 1 bar but doesn’t go up any further thanks to the fan. Keep an eye on your temperature gauge and you’ll soon get used to it. It also takes a while to drop back to normal when moving again.

The easiest way to identify the vent hose to be blocked off is that it is the biggest one of the three. It’s also a good idea to empty the coolant reservoir on the left side of the bike. I don’t see the need to attach a vacuum to the water pump bleed valve as it’s below the level of the filler cap on the radiator and the weight of coolant will push fluid through. Neither does bmw reprom say to do this. That’s not to say that it doesn’t work 😁. I also leave the filler bottle on the ladder connected to the radiator with all the taps openas this adds to the ‘head’ of water and refills any coolant lost in the bleeding process.

It sounds as though you’ve introduced a lot of air into the system. Did you let the master cylinder run dry?  I agree that the abs unit won’t cause that problem. The gs911 allows you to replace the old fluid with new stuff.  If you don’t use it the old fluid remains. If you’re going to do your own work a gs911 is indispensable. Don’t get the cheap copy made in China. It’s loaded from a cd and can’t be updated.
The piston seals should have the pull the pistons back from the disc to stop rubbing

You do not sealer on the clutch cover. I have removed mine twice and re used the same gasket. BMW don’t suggest it’s use. If a chain jump guard is fitted it drops into the seating area of the chain guard which lifts the guard by a small amount. I have just replaced the cam chain/sprockets and noticed the guide protruding from the top of the cylinder head however it was less than the gasket thickness. No harm in removing a small amount from the top of the guide

Genuine BMW Motorcycle Asphaltgrau Met Matt M17

The early models did not have the ‘min-max’ marks on the expansion tank. To get the correct level you have to fill to the bottom edge of the expansion tank filler neck and then draw off 200ml.

On the rear of the expansion tank in front of the power socket there are max and min marks for the coolant level.

You could use a dremel or a half round file to scallop the bar out a bit around the bolt