All this also shows that you are using to much solder on the pins. To have such a solid bridge to used much to much solder. I think you have not trained enough.
But ok now it happens and you must try to solve it otherwise your FC is gone.
Therefore, I recommend practicing with the perfboard and a few pin headers before continuing with the FC. Solder a double row of pins onto the perfboard, just like you did with the FC. Then, create a bridge across at least four pins, just as you did with the FC. Let this area cool down. To remove the solder bridges, if desoldering braid doesn’t work, hold the entire board vertically in one hand so that the solder bridge is at the bottom edge. Position your hand so that you can firmly tap the board with the bottom edge without letting go of the board. Practice this tapping several times. Then heat the solder joint until the solder melts. As soon as the solder is liquid, firmly tap your hand and the board against the work surface. The excess solder should fly off.
SIR YOU ARE REALLY GREAT!! 
Your this method really works and worked well! I Myself Tried this 4-5 times on perfboard, Made solder bridges across 4 pins, And created the Kakute Like condition. I let that cool down, and then i heated it up, Tapped the Perfboard to the work area and The Solder Got Removed fully!!
After some practice, Success each time, I went on to Kakute, firstly Realising that the 355°C will not melt the bridge there (Although 355°C worked fluently for perfboard because it had no ground plane) and so i raised temperature to 410°C, added flux, Solder melted, I very carefully tapped and!! =>
A huge blob of solder fell down and you can see that Majority of it is cleared!
On working on it more, This Finally got resolved! =>https://photos.app.goo.gl/oTDDKzcKd3N4AZqK6
Now only the Inter-GND solder bridge remains, Which will practically not cause any problems.
Still, I will tomorrow further wick the slightly excess solder blob at that Vx pin and It will be done…
Thanks to all of you… you saved a life
Edit: It’s all gone! =>
And finally I got the work done!! =>
You have to double check with an ohmmeter if all shortcut are really gone.
