Best deterrent I’ve experienced is having dogs.
Lived in a beach area that saw lots of property theft and such. In the three years we lived there, literally the only time we ever locked the door was when we evacuated for hurricanes and took the dogs with us. I didn’t even bother carrying a house key because I knew the door was always going to be unlocked. Never once had a problem.
Thieves don’t want to deal with dogs when they could easily just pick a house that doesn’t have dogs.
If the roads are truly highways, you will want to check the laws where you are to confirm if it is legal to ride your bike on those roads. Typically, bikes are not allowed on highways. Regardless, you may want to see if there is an alternate route available. Riding on high speed roads with moderate to heavy traffic is not something I like to do if there is a different option available.
As someone else suggested, a gravel bike may be a good option. Personally I would avoid an e-bike. Nothing wrong with them, but if the goal is to get exercise, then why get a bike that is designed to minimize the amount of work you have to do? It will be tougher in the beginning while you get used to it, but once you do, you’ll be fine.
By far, the single most valuable resource available to new riders is a good local bike store. Find one and talk to them about what you’re trying to do. They’ll be able to make recommendations that are right for you. They’ll also be familiar with the roads in your area and be able to offer good advice about potential routes.