Impact foam seems to me to be the poor man's alchemical feather fall.
Reminds me of this scene from Mission Impossible.
I'll allow the dive through the window, use tail to flick foam into his hand, throw foam, keep diving out the window onto the foam maneuver.
I assume Silas is alright taking a (2d4) damage from window glass in return for getting out of there with Trinia this round?
I believe 20' up is 3d6 damage, Silas failed to negate the first 10' with his Acrobatics check, but the foam reduces that to (1d6) lethal plus (1d6) non-lethal.
If Silas can make a Reflex save equal to 10+the lethal damage, he can cushion Trinia's fall as well (so DC 16 Reflex to negate that 6 lethal, 3 non-lethal to Trinia).
And staying in the room to kill the grappler probably would have gotten him shot by the rogue.
Also, by crashing through the window Silas definitely surprised the sniper outside.
That gives him another round of actions.
Obviously he's going to pick Trinia up and run away, but which route is he going to take?
Staying on the main street, giving him a clear line of run to get away in public, which would allow the rooftop sniper one shot at him as he flees?
Or duck into the side alleys, blocking the sniper's shot and avoiding notice, but potentially running straight into a 5th member of Tark's crew that's been positioned to block off that route of escape (if there is such a man)?
And, assuming he escapes, where is Silas taking the unconscious Trinia?