Lucie - the same goes for the RAF and the RN - you are appointed according to the needs of the service, the individual and then the domestics which come low on the agenda, and you don't always get what you want.
However, I am not convinced that Forces families need huge amounts of support whilst in the UK, as we use the civilian services for most things. SSAFA would not be my first port of call in a crisis. Abroad is different; I use the MoD medical care provided here, and the UKSU liaise between the landlords and those of us in SSFA.
I think you need to quit analysing what you are doing and give it a fair go. The grass is not always greener. Had I moved around, I would not have owned my own home, been able to work nor would ds have stayed in one place until he was 10. I'm enjoying being abroad, but I feel like life is in suspended animation, and will kick in when we move back to UK, and I can get my life and career going again.
I don't know how long your dh is proposing to stay in the Army, but you are putting down roots and will have somewhere to be when he leaves. There are also lots of buzzes about redundancies at the moment, so you will not have to scrabble for housing if he loses his job, or worry about where you are going to go when you have to move out of SFA.
Keep the kids and yourself busy; enjoy the time you have together during the week and change the pace for the weekend when your dh is back. I was more worried about living with dh again when we moved here, as we hadn't lived together for longer than 2.5 years at a stretch than I ever was about weekending. We have now done 3.5 years and I haven't throttled him yet, so it seems to be working.