Also, the fact that your home also has an insane chance of being your coffin..
Edit: here it is: https://upload.wikimedia.org/wikipedia/commons/thumb/a/a3/DS...
The downside to this, of course, being that you'd announce your presence to any competent lookout on the ship you were following.
b) If I was German, I'd definitely prefer to surrender to a western power; I do think it may have been a bit rash to announce my presence in such a spectacular fashion with all the risk that entails, when I could as well have slipped a couple of miles away, surfaced, draped some table linen from the conning tower and radioed my intent to surrender and request instructions; much better than getting rammed or blasted out of the water for my trouble.
c) Three out of four U-boat crewmen got killed during the war, so it could be argued that being on a U-boat had its own risks - besides, this late in the war, the tankers would hardly have had any fuel to ship anyway - the Germans lost their oilfields (primarily in Ploesti, Romania and Maikop, Russia) prior to the endgame and largely relied on synthetic fuels, available in limited quantities.
That being said, I agree with your assessment that the U-boat force had ceased to be a serious threat way before the spring of 1945 - fuel shortages definitely being a major factor.
b) "I also doubt he'd risk surfacing near a foe armed to the teeth so shortly after cessation of hostilities"
Ok. This. I would say, yes, they would risk it on the German side. Germans were known to run to American troops for safety. The 'bad war' wasn't between the US and the Germans. The Germans weren't dumb they knew if they surrendered to the US they would have international rights and be treated like POWs.
c) Sure. But that left each vessel to their own devices. I would imagine many surrendering to the US (but still have arms on board).
"I have no idea how many submarines were still operational and on patrol come V-E Day"
I would say not many. Many due to gasoline restrictions. Being a Uboat wasn't hard, it was being an axis allied gasoline tanker that was hard.
https://en.wikipedia.org/wiki/Submarine_snorkel