Having Apache running on your computer, and the appropriate ports open on your firewall does theoretically make your computer more vulnerable, but in reality it's definitely not a "sure fire way to get hacked". As long as you take appropriate security measures, like having your firewall set up correctly and turning off things such as Server Signature your chances of getting hacked are quite slim. Apache is what powers a large portion of websites across the world, and if it in itself was that vulnerable websites would go down a lot.
Having a dynamic IP will greatly decrease your chances of getting hacked, as well, because it will change each time your modem gets reset, making your virtually un-findable for any would-be hackers. (Unless you use some sort of DynDNS service that is).