He didn't culture bob St Pete, he only needs 750 culture for a border pop.
iron/crab/cow is a good site, but we would probably have problems holding the iron against Gandhi if he decides he wants the tile. Remember Gandhi has elephants now so longbows won't be enough. Building an extra worker directly would probably be cheaper than the extra military we will need to execute a worker steal.
edit: We can hold it provided we run enough artists to get 2 border pops fairly quickly. I think this is worth it if it is still available. This means we might need a 5th worker. Maybe we should go settler-settler-worker-settler.

I'm not entirely confident in my tile-culture understanding, but based on the percentages you posted, I think he's getting 11cpt in Bombay right now, up from 7cpt before St. Pete's border pop.
Spoiler :
St. Pete's initial border pop T285
St. Pete library T302
St. Pete second border pop T312
Tile Culture:
T308 1440: 70% 127-54
T312 1460: 65% 155-83 (7cpt-7cpt)
T315 1475: 67% 236-116 (27cpt-11cpt)
I guess he assigned an artist to combat our culture. If his pace is really that slow, he can't be even close to 750c. Let's say it's somewhere in the neighborhood of 250c - he would need 40t to horse, and we can do a second border pop in 19t of running 1 artist.