Not an expert but I’ve heard the TC and the flex plate need to have some defined clearance so between them. That way when the TC is brought forward to bolt up to flex plate it’s pulled a little bit (1/8”?) away from the trans pump which helps to avoid premature pump wear if the TC pushes hard against the pump
Also heard that the snout on the engine side should be lightly greased (avoids binding) while the pump side snout should be lubricated with trans fluid and not grease (else it will leak)
As to the drive shaft, no idea which is front or back but the donut rubbers must be turned by the engine when going forward so that normal (torsional) drive stresses pass through the thicker part of the donut and not the thinner part. That is the gearbox flange driving bolts turn the donut clockwise through the tick part so it pushes the driven shaft flange bolts that turn the tube clockwise (down the 1/4 mile)
Trust it’s all ok and you’ll be rattle free soon enough