Is it safe to have the Crowdsale and Token contract combined as one contract instead of two separate ones? Are there any drawbacks/advantages of doing this?
Yes, you can do this.
To me, the drawback is that it makes it harder for someone to read your contract and understand it. The crowdsale lasts only a short time, while the token will (hopefully) be used for much longer. It's nice if the token contract is just a token contract. Keeping that code short and simple will make it easier for others to verify that it does what it's supposed to.