Hi. If I understand you correctly you want your SVG exported out of Inkscape with a SET DPI so the line thickness is how you are looking at it on export and it doesn’t seem to matter what format you get it out, so long as it looks as it does in Inkscape right? Have you tried my Inkscape addon yet? It’s designed to ensure svgs are exported ‘AS - IS’ from Inkscape.
Try each SVG option. PDF usually works well if I have layer effects in inkscape that I want to keep. But probably for your purpose of having the right lines based on the screen zoom, maybe the PNG with DPI adjustment will solve your issue.
-s