How many returns does a pool need

I have a 11,000 gallon kidney shape pool with a Marathon 1hp InPower three speed motor and five returns. I recently added a Poolskim USA but it was not performing like I wanted at any speed so capped off two bottom returns. Now my Poolskim is working great and so is my pool's skimmer and The PoolCleaner by Hayward is working much better even at the middle speed.
How can I tell if I am overworking the motor or effecting the water flow rate?
What is the correct number of returns and when or how many top of bottom returns are required in a pool my size?

Reducing the number of returns does not make your pump work harder. In fact it is the opposite. Pumps draw less power with higher head loss so work less.

There is no requirement for the number of returns except you need at least one.

. . . membership upgraded.

I have only 1 return myself and it's fine (Technically, I have 2 more for the solar panels but they are low-pressure, not full pressure as the main one is)

I have a modified Kidney shaped pool with four returns, five if you count the Polaris and two skimmers. My builder said I needed that many to properly stir the pool so that the skimmers would work.