I agree with both the Formula Experience 160 and the Bic Techno formula. I have friends that sail and race both and they do very well. I think the FE 160 will offer better performance overall and they are relatively inexpensive.
The Phantom boards will not offer the same level of excitement or speed as the FE 160, but may be "more relaxing" to sail than formula. They won't plane as quickly either, but they can still get you upwind if the wind drops. Kona's are good light wind boards, easy to sail, good upwind performance, but pretty boring compared to formula.
Don't give me this "not getting any younger" stuff. I am 63 and what keeps me in top shape is knowing that I will be on my F160 30-40 days a year.
Your Deb 70 fin will work well in the light winds, but at 75kg and a 95cm board, you probably could get by on a 66 in winds over 15 knots, which will be a little less demanding and will give you better control. You may lose a little upwind performance, but if you aren't racing, it doesn't matter.
If you don't have an adjustable outhaul, get one. It will make formula sailing a lot more relaxing, allowing the rig to stay in balance as the wind goes up and down.
I think fixing your AHD is a good option too.