Your problems are similar to others and your noted problems may be independent but may also be related.
A) Excess Heat: normally comes from a warn pump or a point of bypassing fluid to tank. If your ambient temps are always high it may be a problem with the water/glycol based fluid (Chemloube) and evaporation of water content. Does your system have any type of heat exchanger?
b) Changing fluid: There is always a lot of concern when changing from a water/glycol based fluid to a synthetic fluid such as the Mobil SHC500 type. The number one problem would be seal compatibility throughout the system. The second problem would be getting all of the water/glycol out of the system.
c) Hydraulic Leaks: Systems utilizing a water/glycol based fluid such as the Chemolube (is this the Chemolube H Special by Hytek?) require seals different than the synthetic fluid noted.
Who is manufacturer of your system? Who is manufacturer of your hydraulic cylinders? How old is your system? Is Chemolube the original fluid from the OEM? have you done a fluid analysis later to check chemistry (mechanical stability) and contamination levels.