I would lower his heels and bars more, so once the frog grows it can touch the ground and pump as nature intended. You can use pine tar for the frog meanwhile.
Pump? As in the old theory that a horse has 5 hearts? Thought that idea was put to bed a while ago. I think it looks like the heels *could* maybe do with being slightly lower, but wouldn't want to say definitely from only those pics. Also considering how painful those frogs are likely to be & how weak his whole heels, if it's been a long term thing, regardless of how 'ideally' you may trim his hooves, he will probably still walk on his toes due to pain. IMO it can sometimes be advisable to leave heels a tad higher while the caudal foot is not strong enough to support the horse.
While maintaining a decent trim is important, IMO the prime consideration should be treating the thrush. I don't know much about DMSO except that it's touted as a 'cure all' including antiseptic, so it could be OK. I don't know about the ongoing use of iodine on such deep thrush, as iodine will damage/inhibit growth of healthy tissue. Also iodine only tends to work on initial application - is deactivated with dirt & such & I'd be wanting something that's going to 'keep on keeping on' better. I'd personally think about soaking in a strong saline solution and using the dry cow ointment or such. The ointment being thick & greasy should stay on the outside for a short time at least & sink in a bit, but in the central sulcus it will remain for some time if the horse isn't in deep mud, etc. It is also non-necrotising, so won't inhibit healthy growth.
Be interesting to see some recent pics, as if your farrier has told you the thrush is under control & you're saying frogs are dry & hard, I'm presuming the pics are pre-treatment? BUT your farrier has also told you thrush is stinky or gooey, which it often is, but not necessarily. It's also not accurate that it will take a frog a year to grow.
As for what you can do to help promote healthy, fast growth, Environment & lifestyle is important. A dry environ & lots of *comfortable* exercise is great, as the more exercise/stimulation, the more growth. It would be best if your horse could be turned out 24/7, particularly if you aren't otherwise able to exercise him daily. Dry environment best if poss. From the point of view of his feet, standing on dry sand would be helpful... but obviously you don't necessarily want your pastures to be decimated to that degree either. When you work him, I'd be inclined to use hoof boots with soft frog pads, to protect his frogs and provide more comfortable stimulation for the recessed heels.
Diet & nutrition are also very important. Well balanced nutrition is one thing. I don't know what Simplify is & it depends what is in your hay & pasture, along with the rest of his diet as to whether he gets the right amounts/mix from the supps to provide balanced nutrition. Feedxl.com is one great source of working out the nuts & bolts of that. I wouldn't be feeding him sweets, but the rest of his diet ingredients may be fine. I notice you soak the coastal hay. Is this because he's overweight or IR, or another reason? Depending on what type of grass, it can be very low in calcium, but alfalfa is high in Ca, so you may find it balances OK.