If the goal is to potentiate the vaped dmt with a little harmalas, maybe have him take the harmalas sublingually. Sublingual administration can offer a quick absorption into the bloodstream/to the brain-mao. I can feel the harmalas working pretty quickly after most of the harmalas are absorbed sublingually.
With smaller dosages of harmala extract done sublingually prior to vaping dmt [or smoking enhanced leaf] , this can be a great way to go aside from changa.
Start low, go up with sublingual harmalas prior to vaping/smoking dmt. A good range imo/e is 20-50mg sublingual, held snuggly under the tongue, & around the 5-10 minute mark most if not all the xtals should be dissolved, with minimal alkaloid aftertaste. I usually will feel them starting to work prior to them being fully absorbed.
Another good way to take harmalas prior to vaping/smoking dmt is just smoking the harmala xtals directly on a small bed of smokeable herb. Smoke directly with a lighter. And yeah, vaping harmalas leaves with low/minimal/no effect compared to smoking them, a highly noticeable difference, night/day. That higher temp's required.
Both of those ways to take harmalas prior to vaping/smoking dmt work incredibly well, and tbh I can somewhat prefer it to changa. It's powerful when done sufficiently
Changa blends like the one your friend smoked, hard to say honestly. A first eye on the ratios you posted for the blend with the amount of harmalas used, that blend seems to be on the lighter end of the spectrum ratio-wise [3:1], unless that is what you were shooting for ..then it's all good.
just some ideas on the matter, though i'd imagine there's other variables at play as well
hope this can help