Here is my opinion.
Is she nutty about the bacon - maybe but she did think of him and it was personal for something he likes so there is thought in it. That goes a long way.
Regarding the splitting of the holiday meals - weird again but I am wondering if she is thinking it will be easier to have you contribute via $ then bring food over and preparing food with a young child. The other thought is this way she is 100% control of her kitchen and then is guaranteed what she wants, even if you can say you contributed. Maybe someone in her past used to rub her nose in, "look what I did for you" type of stuff so this way she feels you don't have to feel indebted to her.
The "why" is what I would like to know. Maybe if you live close, invite her out to coffee and get one of those books that grandparents fill in about stories from their childhood and growing up. I got one for my Dad who I never knew or understood well, and while after he gave it back, not everything was easier, I got him more than I ever did before. You can ask her to fill it out with you. That you want to know her better and are interested in her life so your son always knows his grandma well. People like to talk about themselves, she loves your son, she will probably come at you with some interesting stories.
As far as clothes, I wonder if it was also not a dig at you in some small way. Like showing your Mom that you did not pack well for your son and instead of coming right out with, "Suzie did not pack Johnny enough pants," she said she did not wash them. So while acknowledging her lack of washing, the bigger picture painted was that "Suzie did not pack enough clothes and so I would have had to do a partial wash to keep him clothed properly." If I am learning anything about Southern charm, it is read between the lines and the unspoken is more likely the point then the spoken.
You say they are making a game room now. Finishing something you all can enjoy even if it is a few times a year. That is a huge sign IMO of someone who regrets not being able to do the things she would have wanted for her life and her kid(s) while they were still at the home. I think it is great, please don't get me wrong but if as a Mom, she feels she failed her child(ren) and looks at you as being able to do more, provide better or maybe as a type of mother she is not, that could be why the clothes episode happened.
Passive aggressive way to make herself feel better that you are not perfect.
I will say, count your blessings and I would not even mention it to your husband. So small and from someone who has kids who would love to have grandparents who spent time with them like what you describe, don't risk ruining what good there is for your son.
My ex MIL just told my kids 3 months ago, that she thinks they would have been better people if they had grown up in a small town.
If you knew my kids, you would love them. Everybody does. She is just an insensitive witch most of the time unless it comes to herself and her wants.
I would have traded anything in the world for grandparents who loved my kids enough to make them a priority, bacon and all.
Hope you get some answers to your questions. Look for the why and keep an open mind that we all have our quirks and even if hers might be extreme in some ways, taking the time to understand her more might lead you to a better relationship and a better future for her and your son.
Best wishes!
What a thing to say! Whew. I hope your kids didn't take it too much to heart, but it would be kind of hard not to. 
Listen, don't make something out of nothing. I think all we fellow DIL can do is live and learn and try not to do the same things to our own DIL
I would be insane if I'd take everything my MIL did to heart
