5, use as fodder unless you're new. New players can make plenty of use out of a 0-star SSR. Just convert to fodder once you start having a full grid.
6... probably the same. I don't think that at 1-star it'll be worth it, so keep them separate make use out of the fodder. Use both of them in your grid if new.
7 should make the weapon stronger than LMB SRs, so making a proper weapon of that is recommendable.