Re my "Method" above, and eli-d's reply-
I doubt this method will work since a jpg exported from LR and then imported will open with default settings, i.e. all sliders zeroed,
True.! sliders will be zeroed. I was believing that the OP had "edited" the derivative jpgs in LR with adjusted sliders.
About Resize for Export:
-Setting "Pixels" in the Image Sizing panel is not necessary at all, unless you are wanting specific pixels- say for a web page image. So don't tick "Resize" unless it is wanted.- Simply setting to export as jpg and a quality setting 60-70 will create a compressed image file-size but still contain your original image pixel dimensions.
-Also consider that the Resize pixel dimensions, when given, are only 'maximum limits' for your exported image. They do not distort your image in the way that Photoshop might (without "Constrain Proportions") In LR if you enter 1000x1000 then a landscape image might export at 1000x400 (within the 1000x1000 limits) It will not distort to 1000x1000.
So in summary- For 'Quality' exports- Do not resize, Keep jpg 'Quality' higher up the scale.
You may appreciate this article by Laura Shoe about export jpg quality-