6 opponents is the minimum so I go with that. You get a bit more space with low sea level, less seafood, but there is still a lot of desert.
I tried 2 goes at Great Plains, once I was in the east, with a bad start so I didn't carry on. The second time I was in the middle with huge amounts of cows, a river, floodplains and a fish. And some iron. No health resources available to trade at all, everyone wanted my fish and no-one wanted my cows.
I play with the same opponents as you except I have Asoka in there instead of Saladin. He tends to win the sapce race every time though. I assume we are both playing as Liz?
I've had a bit more tech success by going wheel, pottery, writing, alphabet (trade for agri/AH/mysticism/maths/BW), meditation, priesthood, code of laws, (lightbulb philo), civil service, paper, education (1 lightbulb for about half this tech), (beaten to) liberalism. I pick up other techs needed in trades along the way to get polytheism, literature, drama, music.