do not just see the settlers and initially workable tiles, but also the pop that has to clear those tiles available on your malaria-ridden island...

yes, i am speaking of WORKERS. they are also population - just population in the field!
I agree here. But, I'm less certain about food as king in a flood plain start. There does exist a balance.
Also, if this became a histographic game with the domination victory condition on, then settling on that wheat tile
after the land got cleared might make sense.
Additionally, I think the placement on the banana correct if planning to stay on this island.
This sort of start reminds me of curtatistic's India challenge game, and makes me wonder about a palace swap as
@Lanzelot did in his
playthrough. A palace swap though might get tricky if this ended up high level enough or out for a while (even with pillaging tactics, on some maps those aren't possible until you or your trading partner has Navigation).
Second X from London should go 1NE, to get the Whale(s)?
The X where it stands in the picture has 6 unique squares by my count. The hypothetical X which gets one extra whale has 5 unique squares. A whale gives one extra food, one extra shield, and two extra commerce. The X where it stands thus can grow longer, if using only it's unique squares, while the hypothetical X grows faster and has more production. The extra square from where the X stands is a coast, which has much commerce as a river. So, that's 3 more commerce in a Republic. Thus, the X where it stands has more commerce eventually, once the city has a harbor.
I don't see why extra production would be important for a start like this. I mean this sort or start suggests either a capital swap or a research heavy game. For the former, O. K. then the whale could make more sense (but need a temple or library for that! That doesn't work very well with a palace swap plan!). For a research based game, the X where it stands ends up superior if I calculated everything correctly.