If you notice that you bail a lot when going at speed off the ramps, try changing your setup so that you use softer wheels. This gives you more grip but less effective at powersliding (so designed for vert), also tightening your trucks so they don't wobble as much when you go fast.
For those that use the right analog to gain extra pivot (so you can do 360s on flatland, and 540s etc online) try not to use it to get any extra spin coming off the large ramps as it is a lot harder to judge the right angle for the landing. With the board setup mentioned earlier if you use the natural spin from left analog alone you're a lot more likely to land (and you still easily get enough points to beat the ai).
Also for the scores the highest the ai seems to get is about 17k in the initial rounds. If you're struggling to beat this, try restarting and you can get a luckier spawn with a top score of 14k.