Your question: You operate a jet engine at very low oil level, say 1 QT. Would oil pressure increase noticeably?
How can oil pressure increase if the oil is low? Of course, the oil pressure will decrease and reach 0 when the oil supply will reach 0.
The oil temp is not the critical engine parameter on Jet engines so you should not worry about it too much. The critical parameter on jets is the ITT (Inter Turbine Temp).
On pistons the critical engine parameter is the oil pressure. If the oil supply is low the oil pressure will be low and the oil temp may increase