seam like u did a lot to it. New head, Oil pump/screen and sender, right? Why did u replaced the head, why not just the head gasket? i wonder if the head u replaced actually is a bad one instead, wonder how "new" it is? I am not familiar v cavaliers but i know they all have 4cyl in them, some do Eco-techs some regular once, regardless the reason i asked about the head, is because u mentioned that low press is on all cylinders. I wonder if ur head have evenly wore out components, specifically suspicious about springs. a compression reading isnt always low because of the rings, if valves do not seal well, u will have a low compression as well. That said, what i would do is a wet comp test, but first do dry one (regular one). Then add little oil into a head and see if it raises comp. if it dont, its not the rings which i am guessing not cause i newer seen rings go bad on all cyl at once in a same range. and if its not that then it have to be upper part of engine - its head, since head gasket itself usually lowers compression on one or two cyl, at which it leaks. let me know how it works.