Tube holder: a block that can be used to place 6 chemical tubes on
Fire extinquisher: can put out fire quickly, spraying on players or mobs causes them to get the freezing effect (useful for converting skeletons to stray)
Pesticide: can be used to turn any dirt/grass block into coarse dirt, crafted by pouring pesticide chemicals to the plastic liquid spraying thing that i forgor the name
Plastic bottle: like normal glass bottle but cant hold hot liquid, cant despawn when throw at the ground, throwing at a large water pond will randomly create dead fish, with a chance to be polluted
New effect: contaminated , cant be brewed, food will randomly get polluted with it when exposed near toxic chemical workspace or other chemical uses on environment, player consuming polluted food can get hunger and nausea, contaminated food cant be cooked any further
All the chemistry related things will be your design since i aint no chemist

Not quite QoL, but some good stuff to think about. There are already ideas on the board about what potential plastic bottles could do, so that's the most likely.

Tube holder: a block that can be used to place 6 chemical tubes on

This is a cute idea. Might end up being added on a day where I get tired of working on other things.

Likelihood: 🟠possible

Fire extinquisher: can put out fire quickly, spraying on players or mobs causes them to get the freezing effect (useful for converting skeletons to stray)

A cool idea, but probably not super high priority.

Likelihood: 🟠 not ruled out

Pesticide

There are ideas for DDT, potentially to do with preventing mob spawning.

Likelihood: 🟢 likely

Plastic bottle: like normal glass bottle but cant hold hot liquid, cant despawn when throw at the ground, throwing at a large water pond will randomly create dead fish, with a chance to be polluted

Like I mentioned, there are ideas for plastic bottles, mainly involving more convenient potion usage. The problem is that potions are quite underutilized when playing modded, I think, so its difficult to create a real drive for making and using them. Either way there probably would be some pollution type of thing associated with them, like you suggested.

Likelihood: 🟠possible

New effect: contaminated , cant be brewed, food will randomly get polluted with it when exposed near toxic chemical workspace or other chemical uses on environment, player consuming polluted food can get hunger and nausea, contaminated food cant be cooked any further

Poisoning food is a logical thing to add. The effect you get from it would probably just be the usual effects you get from being exposed to chemicals (so nausea for smelly things, chemical poisoning for acutely toxic substances, etc.), rather than a new effect.

Likelihood: 🟢 quite likely