Agreed on 75 and 4 being plenty big and able to handle the rig. I assume once you come down 75, you're going to take off in Wildwood on the turnpike to go from 75 to 4 in orlando? If so just remember that is a toll road.
In Mobile, stay on I-10 and go through that tunnel. Do not allow the GPS to route you off I-10 to a different tunnel. That other tunnel is only 12' tall, but the one on I-10 is plenty big. It has no Propane restrictions, so you're good there.
Lastly, if you're looking for any overnight spots or places to stay on the way back, i'm in Fort White, FL on a couple of waterfront acres with a single-site campsite on it for friends and family. Here's the link so you can see location and pictures. https://www.hipcamp.com/florida/4a-r...ature-paradise
If you're interested, PM me so I can block the dates so noone books it. I'll make you a deal you can't refuse.