Kubota T1600H with RC44LT deck

Guys,
Just purchased a Kubota T1600H with a RC44LT deck 500+ hours. 3 things that concern me and I was hoping someone can help me.

1) Drive shaft going into the hydrostatic transmission has a little bit of play in it. Very minimal. I hear no noise when using the mower and it functions as it should. Seller suggested replacing the Sub assembly cover (Part#70090-33030) Supposed to be a known problem with the hydrostat on this model. I looked for this part# on the Kubota website and did not reference to anything on the mower however I was told it is an updated part due to the fact that Kubota had issues with the prior model of sub assembly. What are your thoughts?

2) Mower deck is loud + Mower deck has few different rust spots and some gone all the way thru. Can this be patched up? (Pictures attached) Also the middle blade sits about an inch lower than the two on the sides. Looks to me that there is a crack in the metal around the assembly and is getting pushed when in use. What do you suggest for this?

3) Parking brake does not work. Meaning if I press the parking brake nothing happens. How do I check to see what is wrong?

Any help is greatly appreciated.

1) Yes that is a problem with that mower.

2) You can patch the holes but you should replace the deck because if the center problem.

3) follow the parking break cable/linkage and find the breaks. It is either out of adjustment or just wore out.