water flow thru main line 3/4 pex

Need help....

Have a new 5/8 meter flowing 28 gpm at house side of meter, proptery goes up a 10 ft incline to house.

3/4 pex main line 75 ft long,to main valve, a 3/4 gate valve. then 10ft to water.

The 3/4 line runs thru the house for another 70ft. All branch lines to units are 1/2 pex. I have approx. 34 units total as per BMS 79 demand weights chart. 3 bed 21/2 ba 2400 sq ft. single.

Have only 9.0 gpm going thru elct flow meter on water softner, high flow sears 800 softner. I only see a small reduction in flow, maybe 1 gpm with softner on. All plumbing 3/4 pex or copper at these points.. With an oval tub running and 2 sinks and kitchen sink on, the kitchen sink at other end of house flow is about 1/2 gpm...out of kitchen sink.

I am out of water??????

Am I really running out of water or a pinched 3/4 main pipe???..

This is a new house, plumbing contractor playing the blame game on City water dept...I had the city flow the meter rate was 28 gpm...What a chore...No one wants to get involved... Is the 3/4 main too small,is

meter to small