It's time to take stock of the situation. I dominate the land west of the central mountain range. Also on my side of the mountains are the remnants of the French and Russian civilizations, both of whom have previously been defeated soundly and pose no threat. Suleiman has two cities (Ankara and Samsun) on this side of the mountains, but has made no aggressive moves so far and continues to trade and sign research agreements with me. The Greek and Roman lands lie just to the east of the mountains. I have fought defensive wars against both Augustus and Alexander, which demonstrated that my borders with them are secure and easily defended.
I also have a powerful and experienced army. I could take that army and try (and probably succeed) to conquer the world. However, my happiness has just gotten back into positive territory. With the house rules that forbid razing cities, a war of conquest is going to mean a constant battle to keep my people happy.
On the other hand, I could simply rest content with the large and defensible area that I have already conquered. Since I have a solid lead in the score and in literacy, I could concentrate on one of the more peaceful victory conditions. Science or diplomacy victories are clearly well within reason.
Even a cultural victory is not totally impossible. I now have seven active cities: the five that I built myself (Gao, Tombouctu, Jenne, Taghaza, and Tondibi), the former French capital of Paris (which I annexed immediately), and the former Russian capital of Moscow (which I initially puppeted but had to annex recently because of the house rules). That's probably a bit high for getting a cultural victory if you haven't been single-minded about it already, but the Songhai UB contributes extra culture points without a maintenance fee....
In addition, I have seven puppet states (Tours, Marseilles, Troyes, St. Petersburg, Mediolanum, Arretium, and Hallicarnassus). The puppets seem to be making sensible constructions like libraries, banks, and happiness buildings, so they can be left to their own devices.
I'm leaning strongly to switching to builder mode and seeing which of the non-conquest victories provides the best chances.