I'll come at this from a lot of angles. I'm interested.
He could be depressed, anxious, overworked. I know I've phased in and out of wanting to have sex with my wife twice a day to... when I'm low... "wanting" her but knowing that physically it just isn't there. And, a week or two could go by. It takes a lot for me to admit that I'm low, then to admit it to my wife, but it helps. She stopped asking me if I was depressed... She just stays near, let's me know she loves me... And the cycles are much quicker to work through. Once through, it's back to a few times a week.
Also, being a similar age to him, I can attest to that moment when as men, we're realizing we can't and won't ever do what we used to be able to to do, and you being younger... And attractive, he could easily just be feeling like he's not good enough anymore. That's a tough thing to come to terms with individually, but then to work with a spouse through that....
Also, turning 30 is a phase for you, too. You two are in different stages of life psychologically. That's going to be something to remember throughout this.
My wife is waaaaaaaaay more attractive than I am, and she is hit on all the time, and many times by younger guys. I watched her once while shopping... tell a guy she was married. He continued, and I started over to back him off.
She lit him up before I got there. I mean.... Lit. Him. Up.
To see her do that, to feel comfortable that I wasn't going to have to step in because she had my back, for whatever reason, did wonders for the insecurity/psychology of getting older. I didn't have to carry the burden of being with a younger, attractive wife and feel some artificial pressure to satisfy her more.... She had my back and I could simply... Enjoy it without the worry. I was good enough. And, it was hot as hell to watch!
The testosterone test is easy, it's done with other regular tests. I was on it for a few months, and I felt AWESOME! Then, they fixed my thyroid, testosterone regulated, and they took me off. I ask every time I go back to be retested, hoping it's low, so I can go back on. Working out and losing weight was so easy, and obviously, energy in and out of the bedroom was through the roof.
Lastly, you mention foreplay, going down, etc. Is he just refusing? If he hasn't more than once for many years, that could also be an insecurity thing, and if he's already feeling low... He may just not want to continue disappointing you.
The fact that he knows you're not satisfied... That's tough for him, definitely. Be supportive - be transparent. Let him know it's ok to admit some insecurities... On his time...
Good luck.