One other observation regarding the disproportionate high/low readings. The compressor may be weak, perhaps having difficulty creating enough suction/pressure. Just one other angle to consider. Your A/C is not going to blow very cold until you get the low side pressure somewhere closer to 30.

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280