Sorry you've come to this place. I agree with Melissa that your W's suggestions are likely diversions to take the focus off of her, versus things that are really going to work.
The unfortunate truth is that people cannot will themselves to feel sexual desire. When you discuss her lack of desire, it seems to make her defensive, and she's likely to shut you down rather than getting into it with you. If she feels defective, or that you feel there is something wrong with her, it's going to work against you in the long run.
There are a couple paths that people typically try when they find themselves in your situation:
1) Try to become as attractive as possible: There are many resources out there about adopting "alpha male behaviors" and avoiding attraction killers, plus the opportunity to get in better shape, dress better, etc. Unfortunately, I haven't seen a lot of success on this path when you get to the point you're in. It certainly can't hurt, but more often it seems to be a torture-fest where people exert lots of effort with an expectation of some return, which usually doesn't happen. That said, you'll be better positioned if your relationship cannot be healed.
2) Ensure your spouse's needs are met: People tend to withdraw in relationships when their needs are not being met. If their withdrawal doesn't encourage the behavior they want, they get resentful and put a wall up. Unfortunately in marriage this can all happen without voicing any complaints. Another path to pursue is to ensure that you are delivering what your W needs in the way she needs it. "The Five Love Languages" is a good book for you to read in this regard.
If you are hitting the mark, you'll see it in your W's happiness. If you deliver what she needs and she's still not willing to step up for you, you have a real problem -- but I don't think you're there yet.
Looking at your situation, what has happened to you is not all that uncommon. Sex often falls off after kids, and passion often slowly degrades. Your root complaint here is that you feel undesirable. May be work pursuing some IC to see if that feeling can be resolved in ways that don't involve W. (i.e. are you looking for her to provide something that should come from within?)
So all that said, there are two things at play here: (1) having sex, and (2) feeling like W desires you.
If W will work with you on #1, but never again achieve #2, will you be able to find peace?
Acc
Married 18, Together 20, Now Divorced M: 48, W: 50, D: 18, S: 16, D: 12 Bomb Dropped (EA, D): 7/13/11 Start Reconcile: 8/15/11 Bomb Dropped (EA, D): 5/1/2014 (Divorced) In a New Relationship: 3/2015