Well if I got right tire size from Ls web page on the 125 you could get 140lbs in each back tire and 40lbs in each front if using foam and it would cost you about $1 a Pound if shop around so about $360 to have all 4 filled and get bullet proof tires for about 1000hrs of use or more never get a flat or low tire making a 55 gallon drum
ballast is fine for a bigger tractor but on your 125 it's more weight than your class 1 three point can lift also the convenience of not needing a ballast on back and as for using backhoes for ballast is fine short term but if long term you need them frame mounted not hanging on 3 point it will damage it over time especially if doing lots of bumpy driving! If making or using a 3 point ballast on a class 1 or 2 should have some bars or chains going from where top link connected to tractor down to the ballast so you can let it down in a relaxed position not being held up by 3 point! And if your tractor has a front loader with 1k lift capacity and it weighs 1400lbs adding tire ballast should be enough because otherwise your probably lifting too much needs bigger tractor!