Do whatever you can to make sure it's as normal a day as possible.
Staying in HOTAC the night before might well save you travel stress - but sleeping in your own bed may get you a better night's sleep.
Difficult call but it's up to you. (I'd go for HOTAC myself).
If you can get a good night's sleep without a couple of beers then do so - if you can't then think carefully about whether this is the career for you since that is a slippery slope that is all too easy to fall down in this game. Even a couple of beers will show up on your breath when you're saying "Ahhhhhh" to the doc the next morning. He will notice - he won't necessarily mark you down but it won't win you any points if you're marginal on something else. It also won't help your blood pressure.
Avoid caffeine the morning of - that can send your BP up too and whilst it might make you feel better it probably won't help you perform or appear better.
Don't exercise heavily before the medical - Gentle wander round the car park just to relax a bit - ok. 30 min at full chat on the treadmill in the gym at the hotel not ok.
Give yourself plenty of time (as per your traffic remark). it won't do your BP any good nor endear you to the doc if you arrive ten min late sweating like a pig.
Be ready to give a urine sample - i.e drink enough - nothing more stressful than not being able to pee when required. If necessary on arrival ask to give the sample immediately even if your appointment tis not for a while. Most medical staff will understand this if you explain.
If it helps - any dealings i've had with CAA med branch have been fair and reasonable.
They're there to make sure that your fit and safe - they're not looking for a reason to chop you.
Chill out. Relax as much as you can. Be honest. Do not try to bull****. If you're tired after a crap night's sleep because you're nervous - tell him. If you're a bit out of shape admit it and tell them what you're going to do to address it.
Good luck