Has he been checked/MRI'd for cervical or lumbar disc bulges? Stenosis? What about sciatica? Or tendonitis in the foot? Or mortons neuroma? Tarsal tunnel syndrome? Anything in the cervical spine can screw with balance, and anything in the lumbar can mess with feet sensations.
Does he have stress and anxiety (prior to the Dr suggesting ms)? (Dizziness & vertigo related)
Does he have allergies? (Dizziness/vertigo)
Has he been checked by an ENT for inner ear issues, narrow eustachian tubes, ear crystals, or a deviated septum? (All dizziness related)
Does he do a lot of work on the computer? If so, that will cause so many issues its ridiculous.
It irks me that a Dr would suggest MS without exploring other options or at least reserving any judgment before running definitive diagnostics, other than a blood test. I don't mean to irritate anyone who feels compelled to say this, but it won't help to hear "sounds like MS." Thats your biggest concern, and what will keep you both up. Explore the many other possibilities. Pinched nerves (depending on their anatomical placement) can cause dizziness and numbness.
What you need to hear is that these are also symptoms of much lesser problems. They are. I've had them. And I've had MRIs, NCV, EMG, and all manner of bloodwork. And I don't have a disease (thank God - but I've been there mentally...holy s is that terrifying.) I have sciatica, two bulging discs in my neck and lordosis of the spine, which basically just means the curve in my spine ain't great. I also might have an L5/S1 (lower back) bulge, but they need to MRI that area.
Please don't worry yourself sick. And please do NOT let anyone worry you either. NO one. Get an MRI with contrast. That's the thing you need. And when someone tries to scare you with their random story that ends with "but I DID have...." IGNORE IT. Hopefully people on this board will have the good sense not to write such stories, but who knows...
Good luck and please try not to worry too much. I can tell you first hand the worry will eat away at your soul and well being.