(precisionag software geek here)

You have all the data to make right decision, just need to convert it into proper maps. 

Check it out https://docs.geopard.tech/geopard-tutorials/agronomy/variable-rate-seeding-planting-maps I'd suggest also taking slope & topography position index into analysis (on top of yield & field potential maps). 

To make it better for the next years - you can make trial blocks or strips, and calculate then results & profitability per trial block. 

We'll soon make a confidence yield uplift analysis - will be even easier to make good decision.

Try it out for free  & then if needed use cheap pay-as-you go plan. Feel free to send me an email, can help to make it for you.