The important part about the pump is that it should be below the level of the fluid. Doing that insures that it can never drain.Should the pump be level or below the outlet port of the tank?
I don't see how it could be on the supply. Most filter housings I see are 200psi max. If on the return, can it be mounted just prior to entering the tank? I've seen them on the return side of the valve and to me, this would be prone to damage.
The filter at the return is a very acceptable position. In the higher end machines you will find a suction strainer in the tank for the feed to the pump and a filter on the return side to the tank. Position is pretty irrelevant.