I don't know if this is possible inside Inkscape, but if you open the .gpl file in a text editor it's actually readable and easy to edit. Here is an example:
153 153 153 #999999
0 128 0 #008000
211 141 95 #D38D5F
255 0 0 #FF0000
255 127 42 #FF7F2A
The first three columns are the RGB values of the colors. The fourth ...
Inkscape's circles are not Bezier curves. The node tool and many other path editing methods do not work as expected.
Select a circle, apply Path > Object to Path. The circle is now editable path like those you have drawn with the pen. You can add new nodes with the node tool and use all available other path editing methods.
Warning: "Stroke to Path" ...
A little late to the party, but I found that if you Print to File File → Print → Print to File, it works fine. This was on an Ubuntu machine, but this prevented me having to turn the text into un-editable objects.
If you want perfectly smooth curves, then auto tracing a poor quality bitmap is probably not the best way to do it.
Instead, you could manually trace over the lines of the bitmap with the Bézier tool set to apply an ellipse as the Shape in the tool options. This creates a Path Effect. Then you could alter the thickness of the Path Effect by clicking and ...
I have used the LaTeX Previewer for something similar to this. It's an online service so there's nothing to install. It allows you to type in an equation and download an SVG which can then be opened and edited in Inkscape.
For this example shown below, the code I typed into the previewer was as follows:
Then I ...
There isn't a way to change Illustrator's default 72ppi setting, as far as I'm aware.
The problem you are describing has been around for some time, and there are questions about it on the Adobe community site, but still no fix from Adobe. Adobe doesn't currently seem to care about SVG standards, and I wouldn't hold my breath waiting for a fix.
Here's my ...
This may be a small consolation. Whilst I haven't found any easy method to have Illustrator and Inkscape utilise the same DPI system to transfer between each other with SVG's.
I did however find that if I save the Illustrator files in their native .AI format, when opened in Inkscape they will be dimensionally accurate.
If someone finds a better solution ...