Do I need to replace this water pressure valve?
The first thing you should do it check your static (no flow) water pressure and the pressure with water flowing. Find a place where you can attach a pressure gauge and check the pressure with and without flow. You need to find out if this is truly a pressure issue or if the issue is related to restricted flow.

Check the static and flow pressure both upstream and downstream of the filter units. Looking at the pressure drop while water is flowing should tell you if the issue is restriction.

Considerations:

1) the valve he removed is a pressure regulator; regulators are usually installed for a reason (to protect pipes and fixtures from high pressure), if your upstream static pressure is higher than 85 psi (or if your neighbors tell you there are issues with pressure spikes) you should have a regulator.

2) the "set" pressure listed on your old regulator was 45psi, that is pretty low. I would adjust your regulator to no lower than 65psi, no higher than 85psi. The fact that removal of the regulator did not improve conditions makes me think you have a different problem.

3) filters restrict, that is how most work. Chemical filters restrict flow too because they need "residence time" contact between the flowing water and filter media.