I keep telling myself not to post on K1100 threads, which I'm not familiar with, but here she goes.
I'm assuming you've ridden many trouble free kilometres on this bike before the problem started. I'm assuming when you connected the battery, the pump came on, but the engine wasn't cranking. I'm assuming you had multiple attempts of connecting the battery with the same result.
My first thought was there is a short on the positive side which is bypassing the ignition switch. Another thought was has it been stored on the side stand with the handlebar turned hard right, and does the problem disappear when turned the other way, or when straight?
Which lights came on?
The cluster lights came on, they shouldn't, seems to point to a short between the cluster and the ignition switch, or a wire of the same colour.
Another problem is the fuel pump running continuously, it shouldn't. If there were multiple battery connection attempts in a short time frame, the on-off, on-off, results of multiple sparks with contacts could make the tiny fuel relay contacts get hot and sticky. Check if there is continuity between pins 30 and 87, there shouldn't be, if there is, give it a good tap, and try again.
Leave the fuel relay out and the headlight off while checking for a short. You can make a few checks to help isolate the problem. Is there a faint click from the relief relay with the battery connected, there shouldn't be. Do the warning lights turn off with the fuse for the green/yellow, green/black wires removed, they should. Do the lights turn off with the kill switch turned off, they should. This could isolate the problem to a particular wire colour code. Then use a test light to further isolate the problem, say from the cluster back towards the battery, one step at a time.