That sounds like a tall order to me. If I have your question right that's 5 tubes with 32 holes each.

5x32=160 holes total
2000 gallons divided by 160 holes = 12.5 gallons per hole, per hour, to achieve the 2000 gallon goal. Considering the hole size of ".125" 12.5 gallons per hour seems impossible. that would be about 1/4 gallon (0.2083333) per minute.

As for the question if the 1.25 inch main feed line to the manifold being able to provide 2000 gallons of water to the 5 tubes (I assume this is "inside diameter"). Well that just doesn't sound possible to me either. That would require a flow rate of 33.3 gallons "per minute."

2000 gallons divided by 60 minutes= 33.333333

The average garden hose has a inside diameter of about half that (.5, 1/2 inch to .75, 3/4 inch inside diameter). The question I ask myself is can 2 garden hoses (even .75, 3/4 inch) more than completely fill a 32 gallon trash can in one minute. If I remember correctly (I never actually timed it) using one garden hose takes me about 10 to 20 minute to fill a 32 gallon trash can from the garden hose. Cut that in half (using two hoses) 5 to 10 minute. That's at best one fifth of the volume you need. Keep in mind that comparison is also "unrestricted water flow" at between 60 and 90 psi (household water pressure).

So even if the 160 holes could provide 12.5 gallons each per hour (very unlikely), the 1.25 (1 and 1/4 inch main line), the way I see it can't possibly be big enough to supply 33+ gallons per minute to the 5 tubes. Just off the top of my head I would say the whole setup would need to be between 3 and 6 times larger, to supply 2000 gallons per hour (regardless of the pump).

P.S. you can have a pump that puts out 500 psi and only 2 gallons per hour, and on the other side of the coin you can have a pump that puts out 500 gallons per hour, and only has a couple psi of pressure behind it. So it's not really how much psi is required, but how many gallons per hour you need. Unless along with the bare minimum of 2000 gph, you need enough psi to spray the water out of the .125 inch holes a particular distance. Then you would need a pump that can provide a minimum of both (gph and psi).

Get acquainted with centrifugal pump curves as this is what you can buy commercially.

You're going to have to learn to do the fluid mechanics.