Hi Feliz Face, welcome to Pharaoh Heaven.
Many players have completed Baki successfully.
There is one mission (Hetepsenusret) after Baki in the "family history". I haven't finished the "family history" so I don't know what happens at the end.
Prosperity in any mission depends on the overall housing level. One approach is to evolve all houses to a fairly high level, but some players have trouble obtaining enough beer in Baki. Therefore, my recommendation would be to create a few estates (or somewhat more manors). For example, if there are 400 people living in palatial estates (which would be 2 full palatial estates) and 10000 other people (in any kind of houses), then Prosperity should eventually rise to over 70.
Let us know any specific problems that you have. Good luck!