I had an '83 Chevy Malibu Classic that slowly lost power until it was nearly undrivable. I rebuilt or replaced every fuel or spark related item I could think of. I finally had the catalytic converter and O-2 sensor replaced. It ran better, then the problem returned about 8,000 miles later. Disconnecting briefly the exhaust did not help. This suggested that I was sold a new converter for nothing, but the mechanic must have done something to get it to run better.
The question is: what was the problem and what did the mechanic do to improve it?
(hint: I had indications of coolant contamination in the valve covers, any connection?)
I typicaly have problems with repairs that get labled “required” or “needed” when these repairs only seem to make the problem a little less severe. What I am getting at is I do not think you have really found the problem at all. If you had found the problem the fix would have totally eleminated the sympton, sure the sympton could return latter and not be related to the previous repair. When all you can say about a repair is that “it seemed to make it a little better” you have not correctly identified and repaired the problem.
I would certainly work very hard to eliminate any question in regards to if coolant is entering the oil. Until you can say for certain that coolant is not entering the oil you should not attempt other repairs. Make sure your engine does not have a major mechanical issue before proceding on with repairs to the fuel or ignition systems.
The milky emulsion in the valve cover may just from short trip driving. I don’t have any idea what your base problem is.
You need to check the fuel pressure - no matter what has been replaced or when.
You should also check the compression. '83 Malibu? I don’t know how many miles but I wouldn’t be surprised if it just isn’t up to it any more.