I don't know what Cameron is trying to achieve. He has already given us his notice of resignation, to take effect at the end of the current parliament.
I think offering a referendum was his vote-grabbing ploy, hoping that anti-Europeans (of which there are many in older conservative-leaning voters and Daily Mail readers) would put him back in power at the last election, and maybe he thought that if he offered to throw his toys out of the pram, all the other European countries would be willing to put their own interests aside in order to be kinder to the UK (IMO this is less probable). I haven't heard about him pressing for reforms to the CAP, which is not of much interest to most voters, although it is an expensive policy which had its place fifty years ago when Europe was short of food. In some other European countries it is more popular because it is used to prop up rural communities and small towns where lots of people have a smallholding or are small-scale producers with a local farmers co-operative.
Anti-Europeans in all countries often think "in my country we are honest, hard-working people who follow the rules, and all the foreigners are tax-evading crooks with their snouts in the trough" but it is no more true in the UK than it is in other countries. It's just a resentment born of xenophobia. Remember that Brits are foreigners to everyone else.