You can see for yourself now that a hot engine will actually last longer - the hot engine removed the water vapours from the crankcase and not mix with the lubricating oil.
Why do you remove the T-stat in the summers - removing the valve affects both temperature and flow of coolant, the flow of coolant is so fast in a speeding engine that it cannot actually rest and suck the heat from the metal and similarly not shed heat fast enough in the radiator. The stat helps to keep coolant slowed down properly, this also decreases the chance of cavitation (cavitation is what you see as little pits on the waterpump and cooling gallery internals)
If you are facing radiator effeciency issues, be sure that your fan blades are not warped out of shape due to heat, and that the fan shroud is perfectly sealed that it wont suck air from the sides but wholly through the radiator core. If it still is not helping (meaning drinking water on your planet is more like hot bath water) install a multipass radiator - I have these designed myself for Suzuki Bolan, Mehran, and Cultus for the fleets I have contracted. They help in cooling down the engine with considerable efficiency
the breather baffle is spot welded in the valve cover from the inside - I have seen cases where sludge had reduced the opening to 10% of original size, those vehicles were suffering from similar creamy and foamy oil - lack of power and leaking oil seals too.
For PCV valves - buy a new one - suzuki sell it for about Rs 500/-.
You can use 10W40 in your engine but I would check oil pressure at normal temperature - just to be safe.