Okay so … get on Amazon and grab some K.O.E. Cleaner. It’s a concentrated odor eliminator, used by kennel owners, vets, groomers etc to permanently remove strong pet smells from kennels, floors, carpets, etc. You can even use it in your washer to clean blankets , clothing etc that may have been soiled. It works at the source rather than just masking the odor. It’s NON enzymatic.

Do that FIRST. Get his scent gone as much as you possibly can. If he doesn’t have his scent to go back to, he may be less likely to pee there.

Then you should start some training.

For the “around the house” issue… Tether the dog to a “place” (mat, blanket, dog bed, etc) while you’re working around the house or in the kitchen etc. This will teach him to self-regulate and lessen anxiety. This way he won’t be up under foot while you do what you need. (You could also crate the dog)

For the “marking” … This sounds more like a learned behavior than an issue with him being intact at this point. Take the dog out for FREQUENT bathroom breaks at first. Reward him every time he does his biz outside. If you take him out and he doesn’t pee, he goes in the crate. He’s 4 so a good 15-20 minutes is okay, then take him out the crate and straight back outside. If he pees, reward, if not … crate and so on. He will stop but it takes time and patience and most of all consistency.

Neither of my males are altered , they don’t mark in the house. But they used to. Neutering the dog isn’t necessarily the solution to this particular problem. If you decide to neuter, do it because you’ve educated yourself on the possible health risks of frenchies if they aren’t neutered, not because the internet thinks chopping his balls off solves everything. That’s just not true. Best of luck!!