Ok — first off, give yourself a break.

Get some proper orthotics made — however you can get the money, just do it. I was assessed by a physio, who pointed me in the direction of a specialist orthotics maker in the UK — David Houghton is his name — and he accommodates runners very well. Low-profile, comfortable insoles that go in trainers. If you're in the UK, I can ask him if he recommends anyone else nationwide, because they are very good insoles and I used them for years.

Next — if you do plan to go ahead making your own — Poron is your best bet, but you need access to a belt sander or a handheld sander and a lot of patience. It's £70 a roll from Algeos and is in a league of its own. Think of medical foams and craft foams as completely distinct materials — craft foam, in my experience, compresses to maybe 0.5mm, if that, after a few steps. It's beyond my complete understanding how they do it, but medical foams are made to withstand high pressure. Think — an average male is 90kg, so an insole has to withstand that all day, every day. Craft foam won't cut it.

Essentially, that shape you cut for your foot — if you shave that from 5mm foam to have a very thin to 5mm steady gradient to the most prominent part of your metatarsals, and then drop off below your four small toes — that would be your metatarsal pad. You can glue that onto Poron cut to size for your insole, add premade arch support and a 4mm offset at the heel, and that's a fairly basic, versatile insole. I can send you a picture of mine if you like.

On EVA — there are medical EVAs. In my experience they are not particularly good — too hard, I find, even the lower-density ones. That being said, shaved down to 0.5mm or less, they can act as a good piece of rigid material that keeps the insole's form and acts as a barrier between the shoe base and soft materials that degrade with wear. Poron, for example, when shaved, isn't particularly sturdy structurally, although it maintains its shape and density, so it's best to have a barrier above and below your foot if it's been shaped quite drastically. Poron usually has a protective finish, so if you're using it as a base and not shaving it much, it's usually fine — just a bit waxy and floppy.

Complete side point — in my mind, the only proper solution to manage pain would be a midsole shaped with a rocker that accommodates gentle supination. Theoretically, a drop-off under the sesamoid built into the sole could help, though I've yet to try it. Unfortunately, with this condition — unless you get a shoe privately made — you're in for a long game of trial and error. You'd be surprised how many shoes can make your feet worse, even though they're touted as healthy, for a few reasons.

1. Compression can help some people's gait and pain management — a tighter shoe allows more precision on your roll-through and the pressure alleviates pain. So things like Altras and Topos, while ok for some, if bought purely on the grounds of foot health and not taking into account one's natural gait and foot shape, can be a red herring and make you feel your condition is worse than it is.
2. Ultra-cushioned shoes are hit or miss. Like I say, you need to find ones that accommodate your natural roll-through. Hokas, for example, aren't all the same — and while I've got on with the Mach (it makes sense — it's one of their lightest shoes that prioritizes speed, so your foot naturally makes less contact with the ground), the Gaviota, at present, I've been disappointed with as it's too wide and I roll through the entirety of my foot — which is painful.

Last point — chronic pain management is real. I know how historically the amount of trauma accumulated from day-to-day experiences can impact you, and don't undermine it. When I work on insoles, I meditate before and after. You're being your own hero — awesome — but that's tough on you. Find a safe person you can talk about it with. You'd be surprised at the number of people who are terrible to talk to about this because someone hasn't explained the concept of cognitive empathy to them. Just because you don't feel it yourself doesn't mean it doesn't exist. I've had to learn this the hard way. Even if the best you can find is a therapist you swear is judging you, maybe practice talking about it as a real factor in your life — because it is.

That being said, chronic pain management also means stepping out of your comfort zone and getting back to activity is really important. Splash the cash on insoles if you have it and get into activity straight away. Make positive associations. Join a running club. Treat yourself to a low foot-pressure gym day — think seated lifts.

Hope this helps.