Hot water barely coming out of tub faucet, cold water working fine. What could cause that?

Since you say the home set empty since 2007 and the hot side of the jacuzzi is the only hot faucet you are having problems with, the problem could be when the water was turned on for the first time since 2007, there may have been some dirt or grit in the lines and the grit or dirt may have clogged up the faucet area under the knob. It doesn't take much to clog up a faucet. You might turn the water off and remove the hot water handle and check where the water comes in and make sure it isn't clogged up. Give it a good cleaning and see if that helps. If not, there may be a bad or stuck closed valve.