When you say
When importing the file in to Freecad (which is the only way to get the graphics in to Freecad) depending on the zoom the text goes from solid to just the borders.
Do you mean the zoom level at the moment when you import the SVG file? Or do you mean that after you import it into Freecad, and then you zoom it, the text can lose its fill?
If that's the case, that sounds like a bug in Freecad. Based on experience with Inkscape, I would think that's a display issue in Freecad, although of course we would really have no idea about that. If it's a problem with the Freecad display, that means the correct info is there about the text having a fill, and it's just the zoom level makes it seems like it's not filled. But that's huge guess on my part.
I guess you could just avoid zooming, after you import the SVG file. Just import it as the last thing you do, before you send it away. Or there's another free CAD program, called LibreCAD, which you might have better luck with.
When you say
I'm using Freecad to design the enclosure with both enclosure file and graphics file forwarded to a manufacturer
Is the SVG file the graphics file? I'm confused. That sounds like you send them together, at the same time, but separately? Does the SVG have to be imported into Freecad?
I can't answer your question about absolute vs relative coordinates. Are you referring to Inkscape Preferences > Input/Output > SVG Output > Path data ? Unless you know what you're doing, Optimized is the best choice there. Or maybe someone else would have an idea about that. I really don't understand that setting very well.
And finally, I wanted to ask about the trouble you mentioned logging in. Was the forum malfunctioning? If so, please give me details, so I can fix it.