I just tried a fight that ended up this:
Can the black stones be killed? It's whites move.
First, let's assume that white's chain is safe and look at it as tsumego. I tried several sequences but it seems that black is dead:
Second, is this fight naive or realistic? I was just trying to cope with black invasion stone at F3 and tried to seal it. Maybe there is a better approach how to treat it? Let him live peacefully and just build wall on the 4th line?