Broken eggs

I made brownies yesterday. Those who know me well know exactly what that means. I am a stress baker. I do my best to bake stuff that I don't like, because I am also a stress eater. When I make stuff like fudge, or brownies, or cookies, it means I have given up, given in, and am going to have a 10000 calorie day because I suck and I am going to be old, fat, and miserable.
Yeah, that kind of day.
To avoid more massive meltdowns and to keep him under supervision, I had the Monkey helping me. I do try to have fun with it a bit, even if his help mainly consists of adding extra flour and sugar to whatever I am making while I attempt to block, or flapping and hooting with mad joy when I turn on the mixer. This time he added egg cracking to his repertoire, and I picked shells out of the batter. Good times.
I sent him off at last with a beater (Yeah, I know, raw eggs, sugar, all that crap. He licks the floor next to the toilet at the mall too. He is building up his immune system. Shut up.) I cleaned up and put the pan in the oven, poured another cup of coffee and licked the other beater, and bawled my pathetic stupid eyes out.
I always wanted to bake with my kid. I loved it when I was little, and I love the picture of me and my mom baking cookies and making a mess. I love the memories of licking bowls and beaters (apparently they didn't have salmonella or e coli or whatever the hell else we risk these days).
The picture falls a little short of the reality with Monkey. He doesn't hold still that long. Given a chance he will dump all the containers of flour, sugar, milk and whatever else he can get a hold of into a big messy pile. He will eat handfuls of margarine and butter (ugh) and crush eggs in his hands.

 That's my little sensory seeker.
On good days, I can clean up the mess, even smile at his flour covered self and take a picture. Yesterday wasn't such a good day.
He had already had a shower and two baths because he kept removing his diaper or underwear to urinate on his carpet and roll in it, and he had a poop smearing incident that the hubby caught just in time, while it was still confined to just the carpet and himself. It was disheartening after a relatively promising start to his ongoing toilet training regimen, peeing in the toilet with very little encouragement that morning. That was the last cooperative moment of the weekend though.
I can't explain why this hit me so hard yesterday. I just wanted to enjoy the moment, but I couldn't pull away from the frustration and pain.
I know springtime is a frustrating time with our ASD kids, I'm told that regression in behaviour is "normal" in the spring. I just feel so helpless. It feels like any progress we make is pointless, and some new unpleasant or dangerous impulse is immanent even when he is having a good time. He is head banging and punching tile floors again, the bruises and scrapes break my heart to see. He kicks and hits and head butts me until I sport the same bruises and scrapes. Then he just repeats "sorry mummum lub you mummum, sorry mummum" over and over as he huddles under his blanket.
How do I parent here? How do I keep him safe from himself, and keep his sister and me safe from him? How do I watch him closely enough that in the 3 minutes it takes me to change the Kitten's diaper he doesn't somehow shed his undies and spread feces on every toy and surface of his bedroom?
Never mind, I have lots of advice on solutions and strategies and goals and charts and all that to look at. I have tried and crossed off the list many unsuccessful methods, and failed to be consistent enough with others. Sometimes I wonder if I am even close to capable of being a mom, especially to a special needs kid. I want to be the best mom I can be, but maybe my best isn't enough.