You dont neccessarily need to lockntight all the screws. This could make it difficult to dissasemble for maintanence later. Which brings me to maintanence. You obviously have been doing none. Every few runs you need to go through the car and check all the screws. You should check things for excess wear and chaffing.
These arent nikko or tyco cars from walmart or toysRus. They take some TLC even if you are just bashing with them.
As for the uneven were, thats going to happen. It will be almost impossible to stop, even with adjusting the camber. All of these cars have dynamic camber which means as the arm compresses, the camber angle changes. If you want to adjust the static camber tohelp minimize unevem tire wear, there are horazontal rods the go from the bulkheads above the diffs to the outer hub carriers. These may or may not be adjustable. They will have threads on iether end if they are. You can also try rotating your tires if possible.
For the tires just go to amainhobbies.com or one of hundreds of other hobby sites and get direct replacements for what you have.
Hope this helps.