I can see how he could be dizzy. Pulse is rapid enough which means the heart may not be perfusing enough oxygen to the brain which would cause the dizziness. (Having said that though I have a heart condition which puts at that rate and I'm ok, all depends on the individual)
The low BP is also most likely due to the inadequate perfusion. I had the exact same call last year, where are pt barely made it to the ER before he coded.
BLS care is all I would have available to me (ALS 45 mins away). My best option would have been keep him on the monitor, high flow O2, resting, start some lines TKVO, get a good Hx (Cocaine could also be a possibility, dehydration/trauma)and have your partner drive bloody fast to the nearest hospital. I would get everything out and ready for a possible code.