This site will have most if not all the information you need:
http://www.theanalogdept.com/thorens_dept_.htm
I didn't have time to watch more than a few minutes of your videos but the first thing you should do is make sure there is enough oil in the platter bearing. The inner platter either pulls straight up (better to keep turning as you pull up) or you may need to remove a "hook" underneath first. Get the old oil out, foam-tipped swabs are best for this. As lint-free as possible in any case. Use a good engine oil. I've also had success with mineral oil from the medicine cabinet. Exact kind of oil is not critical at this point, as long as it's clean. Just so you have peace of mind while you work on it. You can play around with fancier oils later. About 10 drops into the well, if memory serves, and coat the spindle, too, before you put it back. Again, spin, and give it time, all the air in the well needs to squeeze by that spindle, it can take a good while to settle down. Keep a rag handy to wipe off any excess.
The motor does sound worrisome but it may just need lubrication. You're in luck, your 165 has the protective post next to the drive pulley. Many motor shafts on units that don't have this have been damaged by the platter in transport (ask me how I know), which is bad news.
The pulley contains a spring-loaded felt disc that serves as a clutch. You should be able to push the top portion down to reveal a tiny grub screw in the rim of that brass disc. You'll need a small metric Allen wrench for that. Do press down on the disc as you loosen the screw, otherwise it will get launched by that spring. Take note of how the pieces of the clutch and pulley go together. Now you can apply a tiny bit of thin oil to the motor shaft, and clean the pulley parts.
When you have it back together, don't run it without the outer platter. Instead, put the platter on upside down so you can see what the pulley and belt are doing with all the weight that's supposed to be there.
Adjusting the springs properly is an art in itself but for a start, with the TT unplugged, take the feet and bottom off and prop it up level on books or food cans. There are three springs with nuts for height adjustment. Adjust so the platter (with the mat and an average weight record) floats level, as well. Lots more info at that website above.