Congratulations, Donato! One could have worse problems than this...

I am affraid I cannot offer advice apart from obvious: asking friends in similar position, looking at ads offering jobs (if they still exist ), perhaps asking a headhunter for advice (if they are willing to dispense such kind of specialist knowledge). You could perhaps factor in any special circumstances (e.g. have you resurrected a moribund project for them, do you have a skill unique in the company etc), but then again, three months might be too early for that.

If they originally gave you $5k/yr less than requested, then it looks as if $10k/yr raise would be a safe minimum...

Anyway, good luck!