I've had it with this 904, about to give up!

I went through something very similar to this. I tried different valve body's swam in trans fluid many times, smoked the band etc. I ended up putting a different dipstick in it and found out I was low on fluid the whole time. Some A hole threw a dipstick from who knows what in it before I got the car I got the transmission out of. May seem far fetched but weak 2 & 3 shifts to me is low pressure or low fluid.