Beware the temperatures indicated by the sender are some estimations based on the thermistor table calculations. There is no zero or no other absolute reference in it, so if the tables have errors (they do), the temp indicated on screen can be +/-10-20C difference. Hence is better to double check with a multimeter thermocouple. Or at least by hand, with the filament free you can try pushing down the filament by hand and it should be easy to push. It its hard to push, you should make it easy to psuh, for example increase temp or increase the inner diameter of the most of the zone where the filament passes through, just a little like with +0.2mm increase on 80% of the upper length.
Regarding the hot end, if its teflon with 16mm diameter, you can find a piece of copper pipe with 16mm inner dia usually used for heating radiators, narrow the bottom, and fit the teflon inside that. And then solder with a heat burner some other piece of copper or metal to help attach that to the rest of the extruder. Copper would somewhat help keeping the teflon cool and mechanically rigid, so it wouldnt be bad at all. Anyway its just an idea, and if i understood the situation correctly.
Regarding the hot end, if its teflon with 16mm diameter, you can find a piece of copper pipe with 16mm inner dia usually used for heating radiators, narrow the bottom, and fit the teflon inside that. And then solder with a heat burner some other piece of copper or metal to help attach that to the rest of the extruder. Copper would somewhat help keeping the teflon cool and mechanically rigid, so it wouldnt be bad at all. Anyway its just an idea, and if i understood the situation correctly.