The impact is relative short. So sure maybe we'd engineer 1.0 C and a volcano would add 1.0C. So glaciers would start growing instead of shrinking, rain patterns would return to norms from recent history. The south pole would stabilize, and the major ocean currents would get healthier. I wouldn't expect anything too major though.
Sure if it's bad enough we'd stop adding sulfer and wait for the temp increases to resume.
An increase in ice caps can increase the Earth’s albedo and start a runaway cooling effect. Mass glaciation is a very real possibility.
Most people don’t understand that we’re still in the Quaternary ice age. This is simply an interglacial period. Key geological requirements for mass glaciation continue to hold. The two big ones being the existence of a sufficiently large polar continent and multiple oceans, as opposed to a single large ocean such as during the Pangea period.
Sure if it's bad enough we'd stop adding sulfer and wait for the temp increases to resume.