Well, I have toyed around with the world gen for a bit, and what I can add is there are 3 things that you can adjust to stop the history part where you want. Can do it by megabeast or exact year. If looking to stop on an exact year, it helps to gen the world once and have a long history so you can look into the legends info to find an interesting time to stop it, then re-generate that world, using exact same seed.
One is the exact year it ends, belive default is year 1000.
Two is year to begin checking megabeast percentage, this is the one that usualy causes a world's history to stop. I have only had 1 world run the full 1000 years of history, and that was using the Legendary lands mod, with megabeast paramaters tweaked to help them survive world gen.
Three is what percentage of megabeasts dead to stop at, this is another one that has a big effect on stopping a world early. I have seen 80% of the worlds megabeasts killed off in ~15 years a few times.
Though if you are worried about not having other races, make the number of civilization's higher.
Looking for interesting terrain? Can adjust a few things, like elevation variance, higher means changes can be more drastic over short distances, using the mesh sizes, which tries to clump terrain based on how you weight it, higher values seem to increase likely hood of that range to clump. Also can adjust minimum/desired number of tiles to adjust things to your liking, if you change these, I recomend increasing the maximum number of sub-regions, to make the proccess smoother, even then might need to allow the too many subregions rejection(usualy happens within the first 10 or so rejects)