As for heritability studies, you are certainly right that there is a lot of shoddy work, and by necessity they make a whole lot of wildly simplifying assumptions. If there existed only a handful of such studies, one would be well advised not to take them very seriously. However, the amount of data that has been gathered in recent decades is just too overwhelming to dismiss,

Piling up shoddy evidence does not make good evidence. (And it still doesn't if you -- that's the impersonal "you", not you in particular -- call it "Bayesian evidence".)

especially taking into account that often there have been considerable ideological incentives to support the opposite conclusions.

There are considerable ideological incentives on both sides.

The Sesardic book you recommended is in my university library, but when I went to look at it, I found at least a shelf-foot of books on the subject, some (I could tell just from the authors' names) on one side, some on the other. So I didn't bother looking any further and left all the books there. I could read Sesardic saying what you say he says, but then I could read Kamin arguing the opposite, and in that situation, to form a view of my own with any real basis I'd have to research the subject enough to write a book of my own. I have other things to do. Such is the nature of controversies: they cannot be settled by saying "read this book".

One observation though, that I haven't seen made on either side. Failing to find strong genetic causes for something does not imply that it's the environment; failing to find strong environmental causes does not imply that it's the genes; failing to find either does not imply that it's the interaction of genes and environment. I believe I've seen (but no cites) all three wrong arguments being made from time to time. All that failing to find the causes implies is that we have failed to find the causes.