Well Descent of Angels should be read before Fallen Angels, as Fallen Angels continues on pretty much directly from where Decent of Angels ends. The events of those two novels spread from before The Lion and Caliban are discovered during the great crusade to the beginning of the Heresy. There's also a short story in Tales of Heresy that occurs between the two.
Of those you have there I'd probably go:
1. False Gods
2. Fulgrim
3. Battle of the Abyss
4. Descent of Angels
5. Tales of Heresy
6. Fallen Angels
7. The Primarchs
Other books you should probably pick up are Horus Rising and Galaxy in Flames and I'd argue The First Heretic. Along with False Gods, Horus Rising and Galaxy in Flames form what some would call the 'core' of the series.
In which case the order for me would be:
1. Horus Rising
2. False Gods
3. Galaxy in Flames
4. Fulgrim
5. The First Heretic
6. Battle for the Abyss
7. Descent of Angels
8. Tales of Heresy
9. Fallen Angels
10. The Primarchs
Also it's probably a bit much for your purposes... but
this guide may help with read order in the future.