You're gonna be overmatched; IMO. I don't believe your JD 3005 FEL will be able to lift a 750lb bale over 4ft vertically and stack them 2 high.
I say that, given the fact that the bale will extend more than 4 feet beyond the end of the loader arms. If the entire weight of the bale was at the pins on the loader arm - the FEL would most likely handle the load.
But, extend that weight out 4 feet -- and I have strong reservations that your tractor will pass the test.
And, with that amount of weight extended that far from the front of the tractor; you'll need some serious counterweight -- ballast. I'd want at least double the weight you're attempting to hoist; 1,500lbs, minimum -- and that may exceed the capacity of your 3pt.
My hayin' partner has a 2002, JD790 with the model 70 loader. He's tried workin' with big round bales to feed his 6 head of horses. He's feedin' small squares...
AKfish