I simulated all the circuits that I have on my schematic, but I want to make sure I am not missing anything so I got some components and am testing it. I ran out of mosfets to test the driver stepping up and the relays, so I should that this week.

The 0-10V PWM converter works very well and can be finally regulated. The opto-isolated switches also respond without any visible delay (at least not one I can notice on my DSO handheld oscilloscope, maybe a real professional equipment can see something but should not make that much difference in the end).

Also started looking into reflow oven mods for toaster ovens. I found some projects so far but all them have custom pcbs that are kinda expensive (like Controleo). I have some stm32s laying around maybe I will cook something with it.