I would recommend at least a 160. There will be a slight learning curve. However, if all you do is freeride, then a 160+ will be much better for you in terms of speed, carving, etc. I weigh 175 and my park length is 155, so 153 at your weight is somewhat absurd. After a day or two on an appropriate sized board I believe you will see your riding progress.
Also, when I was about 15 I was sold a 168cm wood core directional board as my first board ever. I weighed probably 140 at the time. So, I definitely know where you are coming from in not being used to a certain stick. It did take me some time to get my stability to a strong level on a better sized board for me, but it was worth it.