re: 1 I say NO to beet juice. If you have BH on, NO beet juice ,according to Kubota. Doubt you'd need juice with BB. Stick in 4WD, low range you should be fine..
re:2 probably not. BX23s has more weight than the MTD SB AND you have 4WD. I'm on my 3rd set of E4s, no real issues with pushing snow...