Fumoffu is wonderful...i watch it over and over and never get tired of it..Ditto the rest of FMP, one of the best series yet..and I have heard there is a sequel..ie fourth season planned but it will take a while to come out. Yes the light novels are finished and translated. They are great as well if you want the story but I am waiting for the anime. The series is a classic and will never get "old" even tho the animation art style is a bit older than many..but it is still very well done with a full range of effects and locations and impact.
Impact really for this series is among the best of any anime series yet. It had wonderful characters who draw you into the story and keep you engaged and caring what happens. And the full range of subjects is addressed: action, suspense, romance, comedy, slice of life even some ecchi and more. In short, it is a real life series and one that shows great maturity and depth on the part of Anime Evolution. I envy you seeing it all for the first time.
It is best to watch Fumoffu between the First Raid and the Second Raid..but really it is ok to watch it after TSR if you want ..or even during as a break in the intensity.
All the main characters have ordeals in the follow up story but they all surmount their challenges in wonderful ways...tho as with any anime any character is 'at risk" as anime writers are much tougher on their characters than many western fiction writers.

Glad you found FMP..enjoy it all.