Im with ya, I've tried just about everything, including 150ml syringes with agar, I'd put them into the pressure cooker and then just shoot them into each cup. But if your like me, you might have more luck with a "no pour method" if your having difficulty, You pour your jars before adding them to the pressure cooker, no more messy hot pouring & spilling. These are the jars I use https://www.amazon.com/Accguan-Silver-Wedding-Magnetic-Kitchen/dp/B08MT5NBS2/ref=mp_s_a_1_3?dchild=1&keywords=4oz%2Bcanning%2Bglass%2Bjars%2Bwith%2Blids&qid=1624650212&sprefix=4oz%2Bcanni&sr=8-3&th=1&psc=1 If you know anyone with baby food jars, those work well too.
we do the same. we add cream, a dash of salt etc to root vegetables, for kale we've been adding fish (cod) for a more savory flavor. If the texture comes out wrong you can use ground flax seed to thicken it.
these are the mason jars we got - it seems like a lot of jars but we really do use them all. slightly cheaper than the target ones. https://www.amazon.com/gp/product/B08MT5NBS2/