question: failing compressor or plugged drier?

Kenmore model 106.77292 top freezer, almost 12 years old, R134a
system, diagnostics so far:

1. lowest refrigerator temp about 50 degrees F
2. lowest freezer temp 26 degrees F, also is temp at evaporator inlet
(after capillary tube)
3. temp of line at compressor suction inlet 84 degrees F
4. temp of line at compressor outlet 109 degrees F
5. defrost heater good at 33 ohms, evap coils NOT iced up
6. defrost thermostat working properly
7. defrost timer working is working properly
8. evap fan and condenser fan both working properly
9. compressor runs fine, but is noisy on startup for about 30 seconds,
has been this way 16
months
10. simple test to suggest not low on R134a: unplugged refrigerator
from wall socket, plugged
back in, took 3 cycles of thermal overload protector for
compressor to restart, suggesting
there is significant high pressure freon.
11. no visual evidence of leaks, i do NOT have a leak detector

anything else i could try?

for further diagnostics, i have one bullet line tap valve. would i
get the best diagnostic usage by
installing on compressor suction or outlet? (instructions are not
clear if i should mount on
copper or steel lines from compressor, i would prefer NOT to mount on
copper line, to save
them for later brazing)

last question: why do driers now come with a schrader valve fitting?
can adequate liquid freon be
injected after evacuation and with compressor NOT running? this
system specs at 4.000 ounces of R134a.

btw, i have the new compressor and drier. was disappointed to learn
that compressor has no oil
in it, from the factory. this compressor needs 280 cc of ester oil.