The Ancient Technology quest (Dawnguard bolt schematics) sent me to Broken Oar Grotto. I just found out that there are several quests that send you there and they can have various problems if you aren't on all of the quests at once.

I have no recent saves to back up to before taking this quest.

Are there any known problems with using the console to "skip" a radiant quest with a bad target location? In particular: additem on the dwarven haul and the schematics, then deliver them to Sorine Jurard. Will that leave any irreversible artifacts, bloating, or damage in my save files?

Not that I know of, in terms of skipping a radiant quest. However, I don't think the additem command will work since it's tied to a quest indicator, and it's a unique spawn...

However, if you haven't already, talk to Jaree-Ra and Ahtar in Solitude and do their quests. Ahtar is the redguard headsman, and he may be in Castle Dour's dungeons. Jaree-Ra is standing near the Alchemist's shop. You should do Jaree-Ra's quest first, as both will end up in Broken Oar Grotto. The only real issue is that it's a possible location for the Moon Amulet quest given by Kharjo; if it's cleared out before you get it, it won't spawn. This is fixed in the Unofficial Patch, but if you don't have that... well, save and track down Kharjo, one of the Khajiit bodyguards for their trading caravans. His route takes him from Dawnstar to Riften, so check the initially Stormcloak-held holds.

Console Commands might be faster, but taking the opportunity to knock out the Broken Oar Grotto's quests is safer and more assured.