Could psychosis be a dopamine re-uptake deficiency? instead of a dopamine excess?

Dopamine reuptake: Given how the receptors work, a Dopamine re-uptake deficiency would lead to a relative Dopamine excess in the synapse. If the pre-synaptic neuron doesn't remove Dopamine from the synapse, it would remain there to stimulate (maybe over-stimulate) the post-synaptic neuron. Dopamine isn't the only neurotransmitter in psychosis, though.

Can be both: Psychosis can develop when Dopamine pathways in the brain transmit more Dopamine than they are used to. You mention two ways this could occur: increasing the Dopamine released and reducing the clearance of dopamine. In fact, when stimulants run the clearance pump backwards surge of Dopamine release results.