I have a '00 K1200RS and a '99 R1100S, very similar brake and fueling systems, mechanically. I've had both problems on one or the other, or both bikes.
Front brake locking - Do you have the OEM (black rubber lines) on the bike?? If so they are way overdue. Galfer or Speigler braided SS PTFE lines for the clutch, front and rear brakes, COMPLETE. AMHIK. It's not the miles it's the years soaking in DOT4 that destroys the OEM lines. Story and pics here: https://www.bmwsporttouring.com/messenger/104113/
Chunks of the decomposing brake line settle into the caliper and make a check valve (see pics) that let pressureand DOT4 into the pistons but not out. THAT is what the problem is. To clear it you have to separate the caliper halves and remove the chunks. Blowing air thru the caliper galleries won't clear it. AMHIK.
Not cranking - Its either spark or fuel. You have spark so check the fuel delivery. You can check the return flow on the fuel lines (from the tank to the fuel rail). If you still have the black plastic fuel line disconnects on the bike you need to replace those with plated brass disconnects: New CPC Chrome Plated Brass noFuel Line Quick Disconnect Set - Oilheads & K-Bikes
The plastic connects are a known problem, cracking and leaking. Save the plastic units to plug into the brass units (after they are installed) to check the flow and return flow. The disconnects have to be mated to flow. They have built in check valve/backflow preventers on both sides. When you are connecting and deconnecting the plastic AND brass connectors push the release button while inserting. Otherwise the "catch" will nick the tiny O-ring and it will not seal and will leak. The brass units come with an extra set of O-rings just for this.
A good return flow (strong flow about the size of a pencil) tells you 1) the pump is pumping and the power is good, 2) the hoses in the tank are OK, not split and leaking, 3) the return line and pressure releif valve are good. If you can hear the pump run and no flow, then you are 95% sure the problem is in the lines in the tank, cracked, split, or disconnected lines. Anything less than strong flow about the size of a pencil indicates it's time for a pressure test on the pump.
A pressure test can be done with the the extra fuel line connector and without removing the tank or pump. Put a 12-18 inch length of fuel tubing on the extra fuel connector (fuel pump side) and a 0-100psi gauge clamped on the other end. Connect this to the fuel lines coming from the TANK. Then turn the ignition key ON but do not crank. The pump should run for about 2 seconds, enough to read the pressure. Less than 45-50 psi means the pump is bad and/or a fuel line is cracked or split and leaking inside the tank.
The return flow test can be done in a similar way by using the extra connector with 12-18 inches of fuel line connected to the return line from the engine.
It's time for those lines to be replaced anyway. Fuel system components for BMW K100
Ethanol gasoline degrades the rubber lines over time and they crack or split.
Use the Oetiker type SS fuel line clamps everywhere. The screw-type fail. It's waaay too much trouble to try to fix this on the side of the road somewhere. AMHIK.