Wowww... I tried for ten minutes (only running and jumping) and only managed to get 1006 points top score. Then I noticed the mode was called "Run & Gun." I could use a gun! Next score was over 6000 :D
Possibly the hardest medium badge I've ever gotten (Or maybe Robot Wants Fishy). It's not comparable with the DJManiax impossible - but still, it beats quite a few hard badges.
Oh btw I think "Lock the bonus" only applies to not being able to change from one bonus into another. Like if you have the blue laser locked and pick up green laser thingies, your weapon will remain the blue laser. If you don't have blue laser locked and pick up green laser thingies, your weapon will become green laser thingies. Even when locked, however, that doesn't mean you can keep the bonus forever - you need the infinity thing to do that.
*Helpful Strategy*
Basically, this strategy centers around the fact that the game can only load up to five enemies at a time (with the load rate of the fifth enemy being very slow). By having a constant four knights / superheroes on the screen (because they cannot leave), this means that there is only one enemy who can ACTUALLY leave the screen and therefore is the only enemy you have to worry about. To kill this enemy, simply lure the knights / superheroes away from the spawn zone until the enemy spawns. Instantly euthanasia / gauntlet him followed by luring the knights / superheroes away again. Because of the slow spawn rate of a fifth enemy, you WILL have a constant supply of mana to euthanasia or gauntlet. Repeat until spawn zone is gone. Then do the same process on the other spawn zones until all spawn zones are gone, and finally kill off the four superheroes/knights you maintained this entire time. Hooray! Hope you found this helpful!