You should have your muffler bearings tested too. i hear if they are worn out they’ll cause the drag on the engine which will not allow it to spin the drivebelt at the required speed. Thus causing your alternator to act like its ‘failing’. Theres a simple solution though; belt dressing will allow it to spin faster and make up for the worn muffler bearing.
shot in the dark, but maybe siezed parking brake? (do you use your ebrake?) i've had it happen twice and it does stink. i cannot remember if it made bad noises though.
if your pinion bearing were bad it wouldn't smell.....
its never just a plastic bag stuck...... that'd be to easy.