On one of our homes we removed several windows and frames then installed glass block. Our purpose was security though rather than critters.

" But seems like, some more rodents have been at it. "

Where do you that? I see a fairly solid basement window. The steel buck was obviously painted and is rusty and will need to be replaced shortly but I see no signs of rodents or critters.

I dont see any sign of critters either. If you are thinking the paint chipping and rot are from rodents, its not. The window could definitely use use some attention though, but, just painting over obvious rust, will not help. Maybe its time, to remove it all, and replace with all new window frame and window.