If the brake pedal is dropping to the floor when you have constant pressure on the pedal at a stop then you have a hydraulic leak inside of your brake master cylinder. Basically a seal on the piston inside the master cylinder is not holding the pressure to each of the wheels and as the pressure drops the pedal drops. That is also why your brakes lock up--there is no pressure to modulate or cushion the engagement of the brakes. You need to have the master cylinder replaced immediately for your own safety.the wear on the tire is because the front suspension is out of alignment. there is a good chance that they never did an alignment when they repaired the control arm problem or, if they did, then the alignment has gone out of spec since then. If the alignment cannot be set to within the factory specifications, there may be other damage that was not repaired from the time of the control arm problem. Tires wear on the inside from excessive "toe-out" or from excessive negative camber. The camber on most front wheel drive cars is not adjustable without doing some modifications and installing a camber kit. More likely your problem is with 'toe-out'. You can experience that by standing with the toes of your shoes facing straight ahead then then turning your right foot to the right so that there is an angle of about 20 degrees. then slide your right foot forward and you'll feel all of the pressure on the inside of your big toe. If you did that for any period of time you'd get a blister inside the ball of your foot because you would wear the skin off. That's the effect of toe-out--you're constantly rubbing off the inside of the tire by pushing against it as your going down the road.have the alignment checked after you replace the master cylinder. In all probablility it can be reset to stop your tire wear. if it cannot be reset within spec then the alignment technician should be able to tell you why it cant be and what repairs are required at that timehope that helps