The thing with cutting steroids isnt about which drug you pick. Its about how the drug is made. Meaning how much solvent and alcohol is added.
I dont have extensive knowledge on brweing but I do know that some esters are much easier to get into high convcntrations than others. The fact that you have painful test e at 250mg/ml is something to be concerned about. 250 is very standard for test e and is very simple to make painless test e at 250mg/ml.
Theres absolutely no reason for that. Most likely too much BA being used in the preparation.
Anway, you can use other drugs to cut the test e but it will only help if the one you choose gives no pain at all. Again, it doesnt matter which drug you choose (aside from test prop), it matters how the specific batch was made.
Mixing any oil based stuff together is ok. Dont mix oil/EO blends. Or straigh EO. Or water obviously.
Lastly, are you sure its the gear and not just pain from the muscle getting stretched out?