If you don’t like the idea of using a larger hook (which will make this cardigan even more holey than it already is), you could instead add repeats of the pattern (usually found between the asterisks) until it is the right size.
The great thing about crochet is that you can easily measure it against yourself (or another cardigan that fits similar to how you want your creation to fit). Unlike knitting, which requires inserting a lifeline and removing your needles, crochet allows you to pull out your hook at any point and take measurements. The tricky part will be understanding (and translating to your size) how they do the decreases and increases while staying in pattern. If you read the sections about shaping carefully, you might be able to translate these exceptions to the pattern over to your size.