Thanks for all your advice.
I started all over with Fossa64-less. If I understand it well, Fossa64-less is much more up to date than the original Fossapup64.
My needs are are few, mostly browsing the net, some music, printing and scanning, reading epub's, keeping passwords, anki (for learning languages), for most of these things I use "portable apps": Midori, Firefox, KeepassXC, Coolreader, Anki.
I installed Simple-scan for scanning and setup cups for printing.
And of course setting up the desktop to my liking.
Everything works as required and I'm happy
I also ordered 2Gb extra ram so I should be good on this Dell E5500.
To finish it off, soon I'll do a remaster so I won't need a savefolder anymore.