Hi Jon,
Welcome to the forum!
I have had (and still have) these tensions and pains for many years. Sometimes it's so bad I can't bend my head forwards, can't look at my feet, especially in the morning. And it gives me a terrible tension headache when it gets too bad.
about the food/pain connection: when you're having food allergies, it's better to avoid the foods that give you more pain. When eating someting you can't tolerate, your body will react and produce toxins that will give you muscle and joint pain. It's a normal reaction, I have a very large amount of food allergies/intolerances.
I think that everyone should get tested for food allergies/intolerances, cause it can cause so many problems.
I see my osteopath when in too much pain, when too much tension in my body. He has 'golden' hands, that give me a lot of relief. He also learned me some fascia therapy exercices, it's very gentle on the body.
When I was in better shape, I did pilates (2 times a week) at a good pilates center (choose a good center or teacher if you decide to do it). Back then, I didn't even have to go and see my osteopath. It built up my muscle strength, kept everything flexible. I would advice it to anyone, but it's hard.
I had to freeze my subsription at the wellness center... I'm so sad about that... but I hope that I'll be able to go back...
Yoga was not bad either, but I overstreched once... be careful with that... and there's many sorts of yoga to choose between. But I preferred pilates.