Yup, that's the correct orientation for both thermostats.
Actually, the fan clutch is supposed to release at higher speeds, when airflow through the radiator is sufficient without the fan turning. If it doesn't release, it could create drag on the water pump, causing insufficient coolant flow.
Try using belt dressing on the fan belt and see if that helps any. (Belt dressing increase friction between the pulley and belt ... a stuck fan clutch could cause the belt to slip in the fan pulley.)
The radiator cap for the same year/engine B300 van should be correct.
To check the lower hose, bring the engine up to temperature at idle and, while watching the hose, have someone bring the RPMs up to a steady mid-range, about 3000 RPM. Hold it steady there for a few minutes and watch if the hose starts to collapse. BE VERY CAREFUL to make sure the vehicle doesn't move while you're down there watching the hose. Also, BEWARE of the fan ... it's basically a whirling set of knives.
Most lower radiator hoses have springs inside the hose or metal rings embedded it the rubber to keep them from collapsing. I'd need the year to look up the correct hose. (19xx/B300/440).
As a rule, if I can't find an OEM spec hose, I use non-specific hoses with the ridges along its length ... those are more resistant to collapse.
BTW - high performance water pumps aren't really necessary in anything other than race engines and constant desert operation.
