I always take oral harmine/harmaline before aerosolized DMT (e-cig juice). It works very fine. The harmine dose is up to you according to how you reel comfortable with it. Recommended is usually in the 100-250mg range (a little lower for harmaline), the higher the dose, the higher the MAO inhibition. For the first time, better start on the low-end dose.
The tyramine containing food is not as important as one might think. These caveats are mostly a legacy from former pharmaceutical MAOIs, which were non-selective (MAO A+B inhibition) and permanent while harmalas are reversible and selective for MAO-A (we usually call them RIMAs rather than MAOIs). This lead to what they called the "cheese syndrome" but it's not much a concern with harmalas. It doesn't mean you should stuff yourself with Parmigiano just before a harmine dose but a moderate amount of tyramine won't hurt you. At worst, excess tyramine will just displace the harmine from its binding site, making it less potent and allowing the MAO tyramine metabolism again (which is anyway also metabolized by the MAO-B in a lesser amount). The risk of accumulating too high level of tyramine in the body is very low with the harmalas as the MAO-A will regain its functions a few hours after intake.
My main rule about food before harmalas is to eat light, digestible, avoiding processed food and fasting 2 hours beforehand. The higher the dose, the more important it would be to apply these rules I think.
Other than food topic, you seem aware of drug interactions you should avoid : SSRIs, MDMA, tramadol, serotonin acting drugs in general as they could lead to serotonin syndrome. That said, a lot of other (pharmaceutical) drugs could be potentiated via the CYP450 inhibition. Among them, caffeine but also various pharmaceutical drugs, according to their metabolism paths. If you're under medication, even if they are not acting on serotonin, you should decrease the usual dose, or in doubt, not take them the day you plan to take harmine.
I'm not sure about your question on the harmine/DMT ratio but it's anyway a good idea to start low with the harmine the first time, just to see how your body reacts. The DMT amount will be the one you want to take according to how you feel comfortable with the experience. You can gradually build you way up with the e-cig, no need for a big unique dose. You could take puffs with few minutes interval and see how it goes, each puff will make you going higher and higher until you decide to stop puffing.
About the timing, you can start puffing the DMT starting from 30-45 minutes after harmine intake but the peak is reached about 1h30 after intake.
