I identify with a lot you say. You could read my thread for more details but basicly me and my wife experimented with swinging, and while we found it hot it was hard for us to find couples that we as a couple matched well with. A few moths ago we decided to try "dating" others on our own. My wife started dating one of the husbands from one of our swinging couples the very next day and I still haven't met anyone....or met anyone willing to date a married man I should say.
I had problems at first with my wife telling me she even had feelings for another man....I don't know what I would have done if she had told me she was in love with him. I am working through those feelings but like you I need more than anything to feel like our relationship is the number 1 priority.
I like you was in the military and am very much an alpha male. With me and my wife the arguments aren't so much over the other man, but over being poly. After allowing my wife to go on two overnight dates I never felt compersion, I hated it. Then my wife tells me she has feelings for the man she is dating. So I tried to play the Veto card and my wife said she couldn't go back to being vanilla. I felt betrayed, and angry that having other relationships was more important to my wife than what we had together and that she'd be willing to trash that if I'm not able to get on board the Poly train.
I think it is easy for people like my wife and your wife (and some of the posters on here that are at the hinge position) to look at people like you and I and say being polys great and you should get on board. They are getting the best of both worlds. I have wondered if the roles were reversed what my wifes reaction to this would have been.
For the majority of our relationship my wife felt the same way I did. Then she goes on a couple of overnight dates and blam all of a sudden she's poly. Then she looks at me and says o.k. you need to be poly also and feel compersion for me when I'm out, when nothing has changed for me. While all this arguing has been going on I told my wife that no one should be seeing anyone else and communication should be kept to a minumum. She agreed saying that she knows we need to fix our relationship problems but everytime we have a good day or two she starts pressuring me about seeing him again and then decides to tell me today that if I take to long to get on board with this that she is going to start resenting me for not allowing her to go be with her "boyfriend". I feel that being poly and having this bf has become a higher priority to my wife than our marriage and am hurt by that.
With all that being said I may or may not be the best person to take advice from but I have a little to offer. I may not be an expert on Poly relationships but I do know that any healthy relationship requires balance and yours is in desparate need for some. It sounds to me like you are doing a whole lot of giving and your wife is doing a whole lot of taking. If you haven't already you and both of the other parts of your checkmark should read "Opening Up" and sit down and write a contract.
I have spent very little time with my wifes bf and had limited conversation, but he doesn't live with me and my wife and I am not very good at maintaning relationships (part of my problem with being poly). Your metamour is living with you boss in your castle. You need to sit him and your wife down and set some boundries. If nothing else at least you saying what you want and then them saying what they want will open the lines of communication up for comprimise.
Either way I would be prepared for a lot of frustration. From my limited dealings with my wife and from what i've read during my research right or wrong many Poly's feel and act like their entitled to this lifestyle. I would imagine your wife is pretty cozy with her situation there and doubt she is gonna react favorably to you trying to set some boundries now seeing as how you haven't set and kept many in the past, but you've got to get some balance back. I also think that if Steve is going to live with you guys and be that much a part of your life he should contribute more to the relationship as a whole and not just be shacked up and sleeping with your wife. Chores, childcare, that sort of thing. Thats my 2 cents. Good luck.