How to approach the dean and/or provost about a years-old two-body problem?
Unfortunately, I doubt this will be easy.  You've already set the precedent that you are willing to work as an adjunct, and the administration is probably hoping that this continues as long as possible.  They might not ever have to hire you long-term, and even if they do they'll at least have saved some money in the meantime.  If they were going to do something out of sympathy for the difficult position you are in, they probably would have already.  That means your only real line of argument is to convince them that hiring you would be better for the university.  This means establishing either that the status quo cannot continue (so keeping you ad an adjunct isn't an option) or that hiring you would be better for the university than keeping you as an adjunct and spending the money on something else.


  In other words, by securing the stability of both "units", one also works toward the stability of the whole.


Your best shot may be if you or your wife gets an offer elsewhere.  This may or may not work, depending on the local culture: at some places, getting outside offers is viewed as a sign of disloyalty.  However, the worst case scenario is having to take the other offer, and it's not clear that that would leave the two of you worse off than you are now.  Without an outside offer, there's no clear evidence of instability.

If you're going to seek other offers, it's probably better to do it soon.  Once your wife has tenure, getting another tenured job (or giving up tenure) would generally be harder than getting a tenure-track job.


  Included in the proposal would be a host of benefits:


I'd focus on the "(badly needed) teaching professor" part.  That sounds like it has the greatest potential for making an argument to the administration that the department is understaffed and really needs this position.  By contrast, they are much less likely to go for the argument that they should hire you on research grounds.