In my opinion you cannot "help" your aikido by weight-lifting.This kind of exercice come in contrast with aikido's principles and instead of soft agile and quick upper body you'll end up with stiff shoulders and arms.The power of aikido is kokyu and tai sabaki,so forget about weights.Nutrition on the other hand is very important i keep it strict myself.Lots of vegetables,rice,sushi,miso soup and absolutely no meat!!You seem to have that part in the right path,so practice on the tatami,keep your diet like that and forget the weights...
Which principles? "Train in the spirit of joy"? "Aikido is love"? Can a strengthened muscle not relax and work efficiently? How much muscular development is too much? Is it good that I can bench press 125lbs just because that is how strong by body is without training in lifting, but bad if I practice and can press 130 next week?
What, exactly, is kokyu, and why does nutrition affect it positively but strength training doesn't? What about having a 600 pound leg press (well, I used to....) is stopping me from using that same leg to step out of the way of a punch?
What is optimal, and why is it optimal, and is that optimization universal or a rather individual matter?