That's not much better!
To be honest, this is on the periphery of my knowledge. But there are some points that resonate. For example, I know what you mean about the change in response when going from a 70mm to 80mm stem, and it feeling kind of vague or ponderous. Sort of feels like your arms are trying to steer the bars into the corners, but your body mass feels like it's trying to push the bars towards the outside of the corner. 70mm (for me) felt more precise, but kept the weight on the front wheel in the old-school way. I'd guess/suggest going to a longer -17⁰ stem might still retain those handling quirks of the 80/90mm stems, unless maybe you can find a 75mm stem and try to split the difference?
In
overall terms, if you were to downsize to a frame with shorter reach - I think it'd want to be a very small change (~10mm at most) or like you say you'll get sat even more upright (which will shift your weight back despite possibly putting more weight on your hands.
From what you describe, it sounds like you like the sizing and front-end response feel of your bike, but are just looking for more trust in the front tyre? (Which generally means you want more weight applied to that wheel)
One alternative worth considering if you're thinking about changing frames and the sizing of your current bike feels good other than lacking a little trust in the front-end, is to try and look for a frame with the same reach but slightly longer chainstays. That way you can setup your body position and steering response the same as your current bike, but you'll get more weight on the front wheel due to the change in weight distribution from the longer chainstays. A few mm at the back end can make a big difference in feel at the front. While it's all the rage to have shortish chainstays in modern XC, these are athletes that live in the pain cave as long as there's a performance advantage. Adding 3-5mm to the chainstays will weight the front wheel noticeably more and help the bike track a smoother arc through corners. The trade offs are it's harder to pop the front wheel up and onto steps and ledges (more noticeably when seated and grinding away, rather than standing where you can throw a bit more body langauge at it...). This sometimes an advantage or disadvantage in tight hairpins. Sometimes it makes the front harder to pop up and flick the bike around, other times it's good because you can get better grip if keeping the front of the ground. Food for thought anyway.