Hmm.... I had him get adjacent to you so that you could hit him back. That was basically to help you. I think we don't have a version of the map now that has the original positions, so I'm not sure I can recreate the precise thing. If you feel I've cheated, I can still recheck and change things.
Also, the direct line that was blocked was the to get out of the swarm. There was a line between the squares the other chimera was in the space its in now.
It also gets iffy when you have a large or larger critter charging. I just handled it so that one of the squares it's filling makes the straight line. That worked for both of them, I think.
In that wording "closest space from which you can attack the opponent", is that the closest space to your original position, or the space closest to the opponent? It's not clear. I might also be mixing up the strict RAW with interpretations we usually use at the table, so...
Now, does shield block only allow blocking for an ally? This gets into the whole "am I my own ally" thing. I think we had it that you can't give yourself actions with White Raven Tactics, or am I misrembering? In any case Shield Block has a number of other clauses, which you can't circumvent anymore. Although, in a PbP...
Ok, let's do it this way: If you feel cheated, you can cheat back. It's too much of a hastle to undo it all.
In any case, do your miss chances on the second guy.