Wow fascinating, thanks for this post Vasco!
I'd be inclined to take a Bayesian approach to this kind of cost-effectiveness modelling, where the "prior evidence" is the estimated impact on lives saved. This is something we have strong reason to believe is good under many world views. Then the "additional evidence" would be the reduction in insect welfare caused by deforestation. I'm just so very uncertain about whether the second one is really a negative effect that I think it would be swamped by the impact on lives saved. This is because we have several steps of major uncertainty: impact of GiveWell charities on deforestation, impact of deforestation on insect welfare, moral weight of insects, baseline welfare of insects (positive or negative).
One issue here is that the same objection could potentially be applied to longtermist-focused charities, but I actually don't think this is true. I think (say) working in government to reduce the risk of biological weapons is actually far more robustly positive than trying to improve insect welfare by reducing deforestation. It also seems like the value of the far future could be far greater than the impact on present-day insects.
What are your thoughts on this approach?
I very much agree with what Kyle said.
Please consider focusing on improving your mental health as priority, because your wellbeing matters, and you deserve to live a flourishing and joyful life.
I also agree that IQ is not particularly important in certain jobs, and there is something impactful for everyone if you enjoy it and your heart is in the right place.
Good luck :)