He's a kid, and kids are annoying at times. They are messy, partially due to lack of coordination. They mature at different ages, and even once they do mature, they will revert back to being immature at various times for various reasons.

Now, that's not to say that everything should be acceptable. A parent's job isn't to be best friends with their kid and make life happy-fun-times all the time. Parents who do that are doing a great disservice to their kids. Those parents raise spoiled, entitled brats that everyone wants to strangle.

This isn't an issue of Mom being a lesbian and lacking a male role model (especially since it sounds like Dad was around enough to keep the kid a considerable amount when you first started dating). This is an overall issue of poor parenting.

Have your talked with your SO about any of this? What does she say? Making the decision to not have food in the car because the kid is too messy is a fair decision. You took away a privilege for the kid and a convenience for Mom to push Mom to parent better and establish boundaries around your stuff. That's an important thing to do if your SO won't listen to your concerns about her child and continues to let him destroy your things.

One thing you need to learn, if you want to stay in this relationship, is to pick your battles. If the boy doesn't like mint toothpaste, then buy the kid-friendly, non-mint kind. Easy fix. That's not something that should be a battle. If it can be fixed witha small change, then do it. Better peace with compromise than standing your ground to win, what, Colgate over Crest?

Also realize that this kid will never be yours and Mom gets final say in your home on how she wants her son raised. If she decides that brushing teeth is too much of a hassle and stops fighting her son, there is nothing you can do. It's her responsibility, not yours, and you can't make up for bad parenting. You CAN walk away from the relationship and wash your hands of it all, which is where your power comes from so long as your SO cares if you leave.

Ultimately, you and SO haven't been physically together that long. Parents have rose-colored glasses for their kids, so your SO thinks her son is the greatest thing ever. You don't have to feel the same way, and very probably won't. Go forward into this relationship with your eyes open. How your SO acts now, and how she responds to your pleas for change and compromise, will shape your relationship. If she won't listen and won't change, then know that what you're dealing with now is what you'll always deal with.

Hi - and Merry Christmas to you. I agree with Lieutenant_dad. You have to compromise and definitely pick your battles. I would also add though, don't let resentments build up. Don't point out every little thing that bothers you but if there's something that could be a real issue for you, speak to your SO about it sooner rather than later. Speak about it calmly and make sure your getting your point across about the issue, not the kid. Good luck to you all!