Ok, I'm a little late to the party, but have skimmed through most and will try to answer some more questions.
As with you being a newbie to tractors, you'd be a newbie to fixing them, a dealer being close to help diagnose is helpful as well. Nothing worse than either having to pay an arm and a leg for shipping or for all your time hauling to a dealer.
You need 4x4 for a tractor as your talking about. HST is also much better for gear for your intended purposes.
The live PTO is all there is today. I have a 50's Farmall Cub, and it doesn't have a live PTO, so when the tractor stops, so does the PTO. ALL new tractors have a live PTO standard.
As far as brand goes, they all have their ups and downs. Not a ton of price difference but depending on how much dealers are willing to negotiate it could make a $1000 difference into a $5000 difference. All tractors will do nearly the same job though, so you don't have to worry that if I don't get tractor XYZ then it won't be able to to what a comparable ZYX does. Biggest difference between brands is your local dealer in my opinion.
I don't think you need a 50HP machine, but it would make a lot of your chores a lot easier.
If you think you absolutely NEED a backhoe, then a
M59 (Kubota 60 HP) or a
L45 (Kubota 45 HP) is the best choice. I'd lean toward the
L45 as I don't think you need all of the
M59. They offer the swivel seat and don't make you get off of the backhoe and back onto the tractor to move it, you can simply "swivel" around as others have mentioned.
If you don't NEED a backhoe and can rent a mini ex for the few times that you will be using a backhoe, then I would say that money would be much better invested in a cab tractor. Your cool when its hot and hot when its cool.