Well... so you want to have some sort of ayahausca trip, not an enhanced DMT vaping trip...
Ok, ayahuasca dosage is not clockwork, beggining with the alcoloid content of the plant... which can change.
During the ceremonies, the shamans would give you an initial cup, and one hour and a half later call for whoever wants to take a second cup. The second cup is enough for most people, but it could be possible that you need a third one or a fourth one (touristic shamans give you smaller amounts, other shamans might give you 3 times as much).
You could do that with your caapi tea, I highly doubt the concentration is as high as the vendor says.
With regard to the ingest of oral DMT... well, the DMT content is chacruna is about 0.1%?... Caapi to chacruna Ratio is 1:1?, I doubt this, I was lucky to watch aya being cooked, chacruna content seemed far less.
So, you could say you need 30mgr of DMT for 30 gr os caapi... or 60mgr of DMT for 60gr of caapi (2gr of 30x extract).
I´m not sure about dmt-chacruna digestion... in aya you take the tea and probably takes some time to digest it, with free based spice I´m not sure... seems more direct, probably a good idea to wait for the caapi to kick in.
Lastly: You mentioned open eyes visuals... aya is not like DMT, it last longer and has some effect on your body.
I recommend you to do ayahuasca with a shaman the first time. It´s not just a drug, it´s an open gate for the spirits, shamans do ending rituals after the ceremony is over, and sometimes perform exorcism during the ceremony, I have seen it.
Also, you might experience things like numbness, decrease in body temperature and yawning, that´s how the spirits enter your body (what people say). And of course, vomiting, diarrea, difficulty in breathing, crying or a lot of nasal mucus... ayahuasca heals your body, it takes bad things out of it, the process can be hard.
"...after five seconds I was no longer a marxist, no longer a materialist, no longer a rationalist.
It killed those things, it cauterized them..."Terrence McKenna