1. Say you and step child get into a disagreement with DH within earshot and step child starts yelling or talking rudely to you. Does DH get involved or does he let you handle it? Do you give consequences or does that fall on DH because he's the parent?

First, neither I nor my bride would tolerate SS to be lippy toward us as individuals nor would we tolerate him being lippy with our spouse.  If he was lippy with me, she would shut him down often before I had to. When he was lippy with his mom he knew that I would not tolerate it.Disagreements are fine. In fact they are great teaching events to give kids clarity on how to communicate effectively and respectfully when dealing with a difference of opinion. Lippy shit from any kid should be met with immediate unpleasant consequences.

Equity life partners are also equity parents to any children in their marital home regardless of kid biology.  That SS was an only child in our home did not negate this absolute fact. I applied consequences as I felt were required for any kid behavior issue.  If my DW did not like how I parented and disciplined then she could step up and get it done before I had to. Or she could have my back and we would discuss any differences of opinion regarding parenting and discipline in private between just the two of us.

In the situation you describe, a skid that would yell at me would find the back of my hand firmly in contact their lips followed by a twisted ear march to their room where they would be firmly planted on their bed and there they would remain until I got tired.

2. What is considered "normal" teen rudeness/moodiness vs unacceptable behavior? Yes I know kids should never be rude BUT I remember being a teen.

Any behavior that violates your standard for kid behavior and performance is unacceptable.  Parent and discipline in accordance with enforcing those standards. Whether your DH agrees or not.  Your home, your standards. DH gets on board of he bites his tongue.

3. Say step child gets into trouble at school or starts failing classes. Does DH include you in brainstorming solutions or does he just discuss these things with BM? Do you go to parent/teacher conferences or just BM/DH? Our school REFUSES to do two separate so DH and BM go together.

Yep, my DW included me in everything Skid related. Our home was the CP household in our blended family adventure and as her equity life partner and as an equity parent in our home I was completely involved.  I attended every Parent/Teacher conference, every Skid school and sports event, I coached his swim team, was an umpire for his little league, I enforced study requirements just as my DW did, together DW and I chose to send SS to Military School for his Jr. and Sr. years of HS and together we paid his tuition and travel costs.  

Doing this was not all that difficult since my DW had full physical and legal custody of SS, we met when SS was 15mos and married the week before he turned 2yo. I have been his dad from nearly the beginning. The SpermClan had COd long distance visitation of 7wks per year.  5wks summer, ~1wk+/- winter and 1wk spring. The only variable was that on alternating years winter break was either from the day school let out until Dec 24 or from Dec 26 until the day before school started. It alternated on even and odd years.  They also could have taken 10days of visitation in our location in late Sept until mid Oct on the condition that SS did not miss school.  This was all COd. They never took that visitation and on a few occasions over the years refused to take any visitation with SS for a year or more.

They never participated in anything to do with SS and school. Never attended any of his notable events including HS graduation, graduation from USAF BMT, etc.... Not even a phone call of congratulations or a graduation card.

In short. I am his dad and I was involved in everything.

To me it makes no sense for someone to be in a marriage that they and their spouse are not complete and total partners in all aspects.  That one, the other, or both of them may have been married before with prior relationship children makes no difference. 

All IMHO and experience of course.

Good luck.

My DH would have jumped in immediately.  In fact, the very first time my SS treated me that way, the hammer would have dropped on him and he would have had consequences from DH.  Needless to say, SS never treated me rudely and we have a good relationship.

It's not your job to parent and you should not have to put up with his kid treating you rudely. It's your DH's job to parent.  Don't let him get out of doing his job, which is to make sure Ben doesn't treat you poorly.