Hi Bill, re brakes, could be one of many problems.
1)Lack of hydraulic oil for PB master cylinders. Later 84 series models had a plastic hydraulic oil reservoir for PB master cylinders.
2)Worn and leaky PB master cylinders.
3)Leaking PB hydraulic lines from master cylinder to wheel cylinders. Remove sheet metal cover over transmission and check for leaks.
4)Most likely, Leaking PB wheel cylinders O-rings.
Do a leak down test, bleed brakes and make sure both brakes are solid before shutting tractor off. Leave tractor a day or two, then before starting engine, test each brake individually to see if one or both have lost their prime.
Re block heater, best is recirculating heater, connect top hose to front of water jacket on exhaust side of engine and bottom hose to drain plug above the starter.
Re starting, are you using the START position on the STOP/START/RUN lever? The decal usually falls off and owners are unaware of START position.