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So, I found this paper:
The Effect of High Nitrogen Pressures On The Habitable Zone and an Appraisal of Greenhouse States
This seems very applicable to
Tohul, a moist greenhouse with a thick nitrogen atmosphere.
I haven't read through it completely yet, but according to the paper, higher nitrogen pressures extend the inner edge of the habitable zone inwards. What's really interesting, and problematic for Tohul, is that moist greenhouses may only be possible around A-type stars, which probably wouldn't last long enough for a sophont race to arise.
If this turns out to be the case, then Tohul may need to be drastically altered.
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I haven't found the rationale behind the limits on moist greenhouse states yet, but the conditions on Tohul are affected by the existence of a biosphere and biogenic particulates, which would affect the albedo and the heat and water budgets.
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From how I understand it, moist greenhouses depend on the amount of water in the atmosphere, and are primarily concerned with planetary temperature. On the other hand, runaway greenhouses seem to trigger from the imbalance of ingoing and outgoing radiation, which occurs at higher temperatures around hotter stars because of the lower near infrared flux, and less efficient stellar absorption.
The result of this is there should be a stellar temperature below which the runaway greenhouse state occurs before the moist greenhouse state, making a moist greenhouse state unstable and short lived in these worlds.
It is possible that temperature inversions may allow for moist greenhouse states around cooler stars, as other studies suggest. It's unclear how these inversions would occur, but biogenic particulates, smog, and photosynthetic skyplankton in the stratosphere of Tohul would certainly make a temp. inversion more likely.
In any case, this study would also suggest that Tohul's atmosphere is too thick for a moist greenhouse to occur at its temperature, so some tweaking to the system might be needed regardless.
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I'm considering some active mechanism that retains heat because of the activity of sky plankton, so that infra-red radiation is reflected during the day and retained at night. Moist greenhouse states would normally be short-lived phases, so it is already necessary to imagine some sort of active mechanism that prolongs the state on a Tohul-like world.
What we want is a mechanism that warms the planet to a certain temperature while preventing a runaway greenhouse from occuring; perhaps if the planet heats up too much the skyplankton might actively cool the surface (by causing rain at might?) thus reducing the water content of the air. Certainly the most undesirable property of a runaway greenhouse is hydrogen loss at the top of the atmosphere, so the top of the atmosphere needs to be kept dry and cool if possible.
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This might be of use when considering biological effects on the atmosphere, the typical "1 billion year until oceans evaporate" may in fact be 2.3 billion years because of how life can regulate atm. pressure and thus the greenhouse effect:
https://www.wired.com/2009/06/earth-gets...extension/
Paper it has info from:
https://www.pnas.org/content/pnas/106/24/9576.full.pdf
