And I also needed to use the + operator just to be able to use the variable. The "Replace Variable" option was greyed out. For reference, here's the tree that works now:

WTF?
I'm going to make my own mission and test this out.
EDIT : Built a test mission and the SEXPs worked exactly as they should have. Directive comes true if you press F (to damage ship B) but nothing happens if you press T (To damage Ship A more). No idea what you're doing wrong, but unless there is more to your event than you're telling me the problem lies somewhere else.
BTW, I did spot a flaw in your mission design. Once you've sorted this problem out both events must include a check that the other one isn't true. Otherwise it's possible for both to come true.
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