Sounds to me like you got the low bid....

How do you know there is enough flow? You need to add up all the GPM of the nozzles, AND THEN determine your supply capacity. Pressure has almost nothing to do with capacity. There is a house in my town with 85 PSI at the hose bib, but can only supply 2 GPM because of a galvanized supply line from the water main.

I would call a sprinkler supply house in your area, and ask them to reccommend a company to come out and take a look.

Connecting two valves to a single output from the controller is iffy at best.

From specifications I can find online, that Toro controller is designed for a maximum output of 0.5 amps per station.

The electrical specifications of some Rainbird valve I could find indicate they have an inrush current of 0.3 amps and a holding current of 0.2 amps.

If you connect two valves to a single output, it will likely work... for a little while.

The holding current of two valve is well within the specs for the controller, but the inrush current of two valves exceeds the listed maximum. But because it only exceeds it by a little bit, it will likely work the first time you try it. But over time, you can be assured that little by little, the electronics of the controller will become damaged.

Your solution is to either find a heftier controller that can handle a larger load, or rig up a relay circuit if your handy with electronics.