I am glad that contact for the kids remains amicable. Your doing the right thing I'm all the right places except legal advice.
Hearing that your so close to retirement, makes sense as to why she is in no rush for a divorce. Right now you are keeping her financially stable.
I know your reluctant to see an attorney, because of what it symbolizes. But it has been said before, you don't have to do anything more than ask advice.
Where you stand now and what the consequences are for you financially if you do nothing, and carry on as you are. Or if there is some other route you can take since you are separated.

I think your fright she is angry and resentful and frustrated. And not one bit of that excuses what she has done,or rather how.
I hear on this forum and others, time and to again of people who want out but won't divorce solely because of the financial implications. I know you don't want to think this far ahead, but don't hobble your own chance of a happy future further down the line by ignoring the opportunity to get sound legal advice.

Who knows, with any luck you won't need it. But better to have it and not need it.
Than need it and not have it.

Keep giving your kids your best. Keep seeing that counsellor.
The forces have an alarmingly high divorce rate, so I would be surprised if you couldn't find a support network of other men and women who have been through or are experiencing the same thing..
No one is saying sit down and compare horror stories, although we all know hearing your not alone helps.
But you could also organise outings or charity events.etc.
Something to give you all a boost.

Sorry if I am jumping ahead here.
I have watched this story over and over so many times, it reAlly saddens me that in the places where support and security matters most there is so little help available.
It isn't just the military, it all the forces. Police, Fire,Paramedics.
Maybe it's just a reflection of the times but it's a sad one if it is.

Keep doing what your doing, one day at a time. All the best.