What's even worse is there's not much room for him either, only a 20 inch (length), 10 inch (width), 13 inch(tall) fish tank.
I plan to line the tank with a soft towel, putting some litter on one side, with food in a bowl and water and hay.
I have soft felt so i might make him a little snuggle tunnel or a tent with felt and string so he can hang around in there.
It'll probably be more cold during the trip, about 50 to 60 in the vehicle..maybe colder (I'm in CT, traveling to SC).
I'm very distraught over the journey.. I know pigs aren't traveling pets and I've read nightmare stories about traveling with pigs.
Any suggestions to what to stick in his tank while traveling that might help him?
Make sure he is not left in a hot car for any length of time. He can stand a little cold if he has lots of bedding and hay in the carrier with him. If it is really cold, take a blanket to throw over his carrier when you open/close the doors.
He will be fine traveling as long as you have a larger cage for him to be put into once you reach your destination. He will not live long in a glass aquarium. C&C grids are great for making a temporary cage (use a tarp or shower curtain for a floor) and don't take up much room in a car.
I've personally only traveled 6 hours. I used a carrier with ventilation and paper bedding (instead of the usual fleece). Food and hay in bowls. Attaching the water bottle to the cage is the biggest mistake I made. Like they said, give him wet veggies and fruits (I used watermelon, cucumber, red leaf lettuce, green peppers) to keep hydrated between stops (when you should offer the water bottle). Never leave him in the car for long, obviously. I think making him a cuddle sack is a great idea! That will give him a place to feel safe. Try to introduce it to him before the drive so he can his smells on it, that might help even more.
We bought 2 hard plastic cat carriers with lots of ventilation and filled them up with a thick layer of paper bedding and lots of hay. We secured them SUPER tightly--seatbelted in, completely packed in by things like bedding, pillows, etc. from all angles. We also had a small cooler with lots of green pepper and cucumber, cold water, and pre-mixed critical care. Every 1-2 hours we would offer them fresh water with a 10mL feeding syringe and give them wet veggies/critical care. We tried to clean out a little of the cage and add more bedding twice during the trip to keep them clean, and added more hay whenever we thought it looked a little sparse.
We only stopped twice for ourselves to get food and gas--this is the thing that I think will be most difficult about your situation, because I would NOT leave a guinea pig alone in the car for very long. Obviously you have to get up and take care of yourself! But I would recommend either bringing a lot of food for yourself, or making sure you plan on drive-through places to minimize the amount of time spend away from the car. I once left my poor husband sitting with them for 30min waiting on my lunch in a rest stop!
I would not use just towels for two reasons: one, it will get dirty quickly, and two, they can bury underneath it and they may overheat if you have the heat on in the car. Be careful about where the airflow is going too--you don't want it to be directly blowing on your guinea pig's cage.
Also the carrier we used is pretty much the same as this one: https://www.chewy.com/frisco-plastic-kennel-almond-black/dp/147321
(It ended up being a great purchase--we now use it for vet visits, and use the top part as a hidey in the cage)