Is it even possible to make this particle effect animation last longer?
Not using the xmls. You could make it last longer if you edit it with the petroglyph particle editor. This is the only petroglyph tool which I don't know anything about.
But instead I'd suggest to <Death_Clone>Damage_Normal,
Particle_Tauri_Nuke_Explosion</Death_Clone> simply insert the explosion particle as new deathclone to replace the old one.
Generally a while ago when I didnt bothered to make own deathclones I used this huge explosion for each ship destruction because it is quite general. You either can search the xmls for the original game particle of the seismic bomb from (was it boba or jango fett)s ability. This version is 40% smaller then the SGMG version and fitts better for smaller explosions.
Do you know what causes this bug?
Models remaining on the field without moving is caused by whether non existent or empty <Death_Clone> tag, or the content of this tag is no valid deathclone instance.
Edit:
In the .xml of the stock BC304s the Deathclone is named
Interceptor4_Frigate_Death_Clone but in all Deathclone tags of all 304 Heroes it is
BC_304_Death_Clone o.O this is what happens when anyone changes names in a inconsequent way. We're going to fix this deathclone bug for the official version thank you. Our Betatester found this bug as well.
I have no idea about the multiple icons bug, maybe its the same bug.