I am running 10.6. Chromium Legacy is for 10.7 and above
Can’t you run 10.7 on that laptop? It seems like you can, and that will greatly improve your software situation. Another thing to consider is to replace the HDD with an SSD. That computer will run any SATA drive (I’ve tested with modern WD blue drives), just grab something like 250GB for 30€ and enjoy speed.
There was also another user who gave me a link to some software that modifies mixed-mode ISOs so that they will boot on my potato laptop.
Yes but Debian provides that out-of-the-box and officially supported. That means everything will work fine and as stable as Debian is usually.