It sounds to me like your duct system has leaks that cold air is getting into your system. Even if your ductwork is in concrete it should not drop your air temp that much unless cold air is getting in also. I would start with temperature readings of the return air temp at the return compared to the actual return air temp at the furnace. I would then check the supply temp at the furnace right after being heated and compare it to the supply temp. You might have to put some small holes in at the furnace so don't forget to seal them.

I also vote no to the plastic liner. hard to clean and wasteful to just replace them all the time. Nylon curtains can be thrown in the wash and bleached (it's easier to wash them routinely though, before the bottom hem gets moldy). I use this kind of hook which makes that chore super easy. I used to have two curtains doubled up on regular hooks and that worked just fine, btw. double sided hooks or double rods are not really necessary unless you just like the way it looks.

The fire in the garage smoldered for over 30 minutes, filling the apartment with dense smoke. The heat right on the other side of that long wall to this apartment was intense and may have melted things in wall like plumbing and Romex wiring. They need to be opened to see. The upper floor of the apartment was smoking out of the electrical sockets, out the recessed lighting and the heat even permanently yellowed the fiberglass tub up there. The smoke is in the walls. If they want to gut, I'm letting them gut.

Jennifer, I think you know the issue here is more psychologically-related than interior design-related. My advice to you is to keep your goals inline with your values. As Donald said above: "If you want to be the kind of family that eats dinner at the table together every night then start doing it now." You're drawn to a minimalist decor? Make it happen. You start with the list of essential functions in your space (sleeping, working, eating, relaxing) then you equip each area accordingly. Nothing more. Which means you get rid of what doesn't serve one of these purposes. You mention you're a hoarder: find a way to stop that behaviour or else it could consume you and negatively impact your relationships. Things don't provide lasting soul-nourishing happiness. Relationship and experiences do. Chances are high your kid won't be interested in your childhood toys. Keep your top 5 favourite ones if you must, but no more than can fit on a small shelf. Boxes and boxes of makeup? Whatever for? You only have one face and makeup breeds bacteria so quickly. Delete Letgo and similar apps if they tempt you to buy random stuff you don't need. Instead of scrolling apps for random stuff to buy, do something else, for example, listening to short motivation inspiration videos like Mel Robbins, cleaning or exercising, etc. Any distraction to help you stay on course. Once you control the clutter, your space will make a lot more sense to you and decorating it will be easier. You can do this, Jennifer! :)