"My husband shouldn't have to discipline him"

Umm yes he should, he is SS's parent. You need to let your DH know that you can't help take care of SS when he is not present because he does not respect or abide by your rules.

You are allowing SS and DH to manipulate you into thinking you are somehow responsible for all of this. You are not!

OP you've got ALOT of anger it feels like. Understandable your SS sounds like a brat.

Your partner needs to step up. It's clear the child doesn't respect you as an adult / guardian. If he doesn't then it's DH's problem. Either he get's the kid to behave and obey you or he takes over the roll because no you shouldn't be the only one doing this.

Think about what your partner would be doing if you weren't around and he had to deal with the kid alone?

Been through this.

1) "...now he wants a cell phone for Christmas. I in no way feel he deserves a cell phone..."
Not your decision or worry. If your DH ends up getting one anyway (and he likely will) then make sure your plan is SEPARATE from his in all ways. I refuse to be on a combined plan with DH and the SDs (and one that BM has access to as well).

2) "...and quite frankly am shocked he would ask for one he is flunking half his classes at school, he can't keep his room clean his only chore, he is grounded for bad grades..."
Ignore. Not your issue. Do not monitor this. I would only make sure DH took care of the room cleaning if it smelled or was going to cause problems with your lease/deposit - which I assume is partly your money.

3) "...which is punishment to me because he is home with me on weekends and he is in my face antagonizing me all day."
Stop agreeing to watch him on weekends. If it's DH's time, either DH should be there or making other arrangements. I do this/did this with SDs at first at odd times but quickly understood it can go bad fast. I not only do it when I want to or if there's truly a reason DH cannot. If it's because of a REGULAR work schedule then things should be switched up or your DH needs an alternative.

4) "Yesterday, breakfast is cereal and fruit. He won't eat it because at school he gets burritos and pizza for breakfast."
Fine, then he doesn't eat breakfast at your house. It's his choice, make it clear that he refuses to eat what you serve, there's no alternative. Done.

5) "I take him with me to the park for a walk. He acts like an a-hole the whole time. Throws rocks around windows and vehicles. My whole peaceful walk was ruined because all I do is bitch at him stop this stop that do this do that."
No more walks. The first rock thrown you turn around and leave for home.
Your expectations IF you are with him as the adult must be crystal clear and ramifications instant. He goes to his room.

6) "Then while I am making dinner I ask him to read or do homework in his room as he is grounded for being an F student. He refuses and instead continues to act like an a-hole in the small apartment we live in. He jumps around in the living room swinging a toy like object. Is in my face asking me a thousand questions just antagonizing me to the point I just start shutting down.I am like get away from me and he won't."
You can ask him to do his homework, but you can't make him do it. So either don't ask or ignore it. As for the jumping/recklessness inside, no tolerance. It's not a gym. He can get hurt. Into his room. He's antagonizing you because he knows it works. Show no emotion. Tell him to stop. Be clear about expectations/ramifications. If he doesn't, then into his room.

7) "SS does a 180 when dad is home being good kissing up to his dad. I literally want to hit him but I know I can't. My husband shouldn't have to discipline him. I just can't control him. I am not his mother..."
Of course...because his dad doesn't discipline. YES he SHOULD. It's being a parent. This is your ultimate problem. I'm betting your DH sees you as nothing but complaining and being mean. You need to have a calm, rational discussion with your DH (alone, no SS there) about YOUR situation - no pointing fingers, no insults, no "but if you did..." Have a plan. Remain calm. If your DH and your cannot get onto the same page, then you'll have issues. Have you tried recording your SS doing any of this? So your DH can see what he's doing? Or would your DH simply turn this on you?

I'm not saying my DH and I did, or do, see eye to eye, but we can at least discuss things and I can tell him what I will or won't do without over-reacting (at least most of the time). It took some list-making and thinking before acting but it's doable.

Disengage Hon and stop trying to parent him, he's not your kid and not your responsibility...

Then get a Nanny cam so you can record him and show Daddy what a nice child he has when he's not around, after you showed DH the video you smile and say and this is the reason I'm not going to look after him anymore, if you are not here SS will not be here, he can go to BM's, Grandparents, DAycare what ever, but I'm not responsible for your son anymore...... I might change my mind when he starts behaving..