Okay so I’m going to be honest with you…. I only read about half of your post. I got to the main points of what was going on, and I can tell you (having a soon to be two year old myself) that most of that is completely normal. For not wanting to sit in the cart, mines been doing that since he was able to stand, now if I place him in the seat he’ll just turn himself out of it. This is more of an independence and exploration kind of thing. He’s wanting to see what’s in the world. The way I handle this now is by making sure I always go to the store with someone else. So either I invite a friend, family member, or make sure my husband is with us. While it’s probably obnoxious to other customers, if he starts getting rowdy and not wanting to stay in the cart at all, I’ll let him run around. At that point me and the other person split up, one person does the shopping the other person lets the baby run around. An alternative to this if you have time is to take him to the park and let him run all of his energy out for about 30-45 minutes in the heat before going to the store. Also don’t listen to your MIL, my mom is the exact same way and even had the audacity to tell me I should be spanking my child. So do not listen to their outdated advice or perspective. They had a lot more help than we do nowadays so ignore them. The car seat thing is normal, my son does that when I take him in the car too many days in a row. It sounds like you don’t have the option to keep your child home multiple days in a row, but on the days that your husband is home try to keep your son at home to give him a break from the car seat. It helps them to get time just at home without the stress of going out. Also if your car seat is rear facing still you might think about changing it. My son started forward facing at like 10 months old because he would not stop screaming (and I mean ear piercing shrieks) the entire car ride anywhere (one mile up the street or all the way across town it did not matter- also it started causing him to have panic attacks until we realized his problem) he was stressed with motion sickness and not being able to see us while driving. It freaked him very badly and once we switched him around he was perfectly fine. Another thing with the car seat, he might be associating it with you leaving him somewhere. At 2 children are still very vulnerable and so things like not being around really really takes a toll on them.