You can remove the drive fairly easily if you have a high temp heat gun or a small pin point butane torch to heat the swing arm pivot pin pins to about 120°c or 248°f. Never try to remove those pivot pins cold or you risk stripping the threads out of the alloy swing arm. Try to keep the heat off of the swing arm paint as you can discolor it if you are not careful with heat placement.
You can re-torque without special tools if you first torque the adjustable pivot pin to proper torque then mark the exposed pin so you can assure that it lines back up and stays lined up as you torque the outer lock nut. Or initially tighten the outer nut with a box end wrench while holding the properly torqued and marked pivot pin, then do the final torque with a torque wrench. Takes a little fiddling but is definitely doable without a special cut-away socket.
Book calls for 7 nm pivot pin torque but that is too low for the adjustable pivot pin with the drive weight hanging on the swing arm. 10 nm has worked much better for me.
Your leak is more than likely the pinion seal as those do seem to seep a bit on the old 1100 bikes.
Installing a pinion seal in the 1100 final drive is a bit of a PITA chore if you haven’t done one before as you need to find, or build, a way to hold the final drive securely and keep the ring gear spool from turning while you break the pinion nut loose with a deep 36mm socket. The first one that I did years ago I just bolted the rear wheel back on the removed final drive then set the drive on my shop floor with wheel side down on an old blanket. It worked but I had a dickens of a time keeping the entire drive from spinning as I cranked on that very tight pinion nut.
The deep socket needs to have enough internal clearance to clear and not damage the pinion splines. Then next you need to remove the somewhat difficult to remove threaded pinion seal ring.
To remove or reinstall that threaded pinion seal ring you will need a special deep pin socket that fits the threaded seal ring slots. Years ago I made a special pin socket from an old Chevy 4wheel drive front wheel bearing nut socket. It didn’t take a lot of work to do that but I needed to weld on a plate so I could use a torque wrench on the socket for the seal ring re-installation torqueing. You might need some heat to get that seal ring to come loose.
Just be sure that you use proper sealing Locktite on the squeaky clean threaded parts like the pinion nut and sealing ring threads or gear oil can seep past those threaded joints.
You can install the crown bearing seal without disassembling the drive by drilling a couple of very shallow small holes in the seal, then screwing in a couple of sheet metal screws, either prying on the screws over a fulcrum or using side cutter pliers on the screws over a soft fulcrum. Then just install the new seal using the old removed seal as a driver by reversing the removed seal and using it as a seal driver.
As I mentioned above those old 1100 final drive pinion seals do seem to seep a bit, especially during extended storage, and even more so if the gear oil in the drive is synthetic.
My guess is that if you remove the boot clamps, then clean most of the gear oil out of the boot best possible with the boot in place, reinstall the boot clamps, change the gear oil to a conventional 80w90 non synthetic gear oil, that your pinion seep will mostly, or even completely, go away.
At least a good easy step to try before tackling that PITA pinion seal replacement.