Sorry to hear about the accident. Get copies of all police reports and if the guy hesitates to pay up, press charges and get a lawyer.

Iv'e owned my 82 300TD since 1990. I average about 24 MPG so your not completely off.

Test your speedo with either one of the radar speed detectors on the side of the road. Here in Texas they are putting the speed readouts just as you enter school zones here. Texas is VERY serious about school speed zones. Everyone will slow to 20MPH BEFORE entering the zone. Fines are very very heavy.
Or get on the highway. Do exactly 60MPH and time yourself between 2 mile markers. It shoudl take exactly 60 seconds between the 2.

44PSI is high based on Mercedes info. I run ar 32psi on all 4 tires. Which is still high.

The engine temp is a little high. Based on the outside temp, the cooling system should be able to maintain the 80C area. Try a IR temp gauge and see what the radiato is doing temp wise. If the radiator is clogging up. The IR temp sensor will be able to determine that. If its OK test the thermostat in a pan of water on the store with a thermometer. It should be fully open at
80C. If bad replace it.

Dave

__________________
1970 220D, owned 1980-1990
1980 240D, owned 1990-1992
1982 300TD, owned 1992-1993
1986 300SDL, owned 1993-2004
1999 E300, owned 1999-2003
1982 300TD, 213,880mi, owned since Nov 18, 1991- Aug 4, 2010 SOLD
1988 560SL, 100,000mi, owned since 1995
1965 Mustang Fastback Mileage Unknown(My sons)
1983 240D, 176,000mi (My daughers) owned since 2004
2007 Honda Accord EX-L I4 auto, the new daily driver
1985 300D 264,000mi Son's new daily driver.(sold)
2008 Hyundai Tiberon. Daughters new car