I guess you guys checked out our health and safety section? It has some relevant comments regarding dark trips and integration.

as for your other questions:

Aya needs to involve the oral intake of a brew that contains Caapi.  For similar effects, caapi can be substituted by another MAOI like syrian rue but thats not really considered ayahuasca, maybe others can call it an ayahuasca analogue (or anahuasca), or similar.   Often the caapi brew will have a dmt-containing admixture, and more often than not ayahuasca is the name of the brew with both MAOI and DMT, but it can be just caapi too.

You could smoke DMT on top of ayahuasca/caapi/MAOI brew, and that would extend/change the trip indeed.

As for handling several hours of aya trip, well you can always start with a low dose. Check out the FAQ for more info and useful links on aya, brewing, dosaging and consumption.   Do run a search here in the forum for "headers" containing "ayahuasca vs freebase" or "ayahuasca dmt" or "oral vs smoked" or similar keywords, im sure youll come up with a lot of threads discussing comparisons

Be well