Check the brake vacuum piping, start at the servo, look/ feel for splits at all ends/joints right up to the inlet manifold. There will be a one way plastic valve half way and the piping often splits there too. The hard pipe splits longitudinally from an end, of you can move/ rotate the pipe from the joint, it is splitand allowing air into the intake manifold, upsetting the petrol/air ratio.
This causes loss of power and stalling issues particularly when pressing the brake pedal which might go "hard" prematurely.
Gradients and accel/decel will rock the engine and the piping move, any splits open up.
As for windows ,check loom condition in the rubber gaitors between the doors and pillars, pull the gaitos back and inspect. Check all doors.
Both issues are inevitable with age.