Couple of Questions on 1980 300D

[tex599]

New to me, 1980 300d and a couple of more questions.

What is the normal operating temp on this car? It seems to run at 100c and sometimes a little above that when cruising down the highway at 75mph. It will sometimes drop below 100c while stopped at light, etc. . . It has been hot in Texas, 106 today. Is this the normal operating temp, AC works great as well. AUX fan works to.

I don't have an RPM gauge, but my RPM seem high at 75, it is shifting into 4th gear. Is this normal?

Last night pulled the car in the garage to inspect more stuff under the hood, noticed smoke coming from below the air filter housing. Removed housing and the Crankcase or PCV was disconnected. Should there have been a clamp on this hose? I went ahead and added it.

Is the MB coolant or Z-05 green in color or is this just regular old coolant?

New to this car, so just still trying to figure it out.

Thanks,

Tex