your worried about HIM finding your IP? then your fine for the most part.
im a certified/licensed Network/Desktop Admin/tech, so take my word for it
few reasons why:
1. the biggest reason. 99% of the US population has absolutely no clue what to do with an IP address, even if they DO get it. he would see numbers but have no clue wtf they ment. and the IP he gathered wouldnt direct strait to you, but instead to one of the routers you connect to through your ISP more than likely
for instance, if the mods of this website traced my IP, it wouldnt pinpoint them strait to my house, but instead to a sprint server/router located a good couple miles away from me.
Finally, even if he DID trace it, and it DID go to my house, then he has to go through the trouble of finding out WHO lives in that house, and also know your name to know its you. youd be surprised how many people dont know how to use google, and would never accomplish this, not to mention alot of peoples home addresses dont link to a name. Now, if you posted from work, then i suppose IF it led directly to your location and not a router, he would know that its your job (since hes been bashing you appearently, he should know where you work) and know its you, but theres alot of "IF's" that are less than likely to happen.
long story short, who cares if he gets your IP, the best he will know is that your located in the same 100 mile radius of him
2. if your posting on a blog, he will have no way of gathering your IP without A. having some type of administration power to the site (this happens with forums, not so much blogs) or B. actually "Hacking" the hostings servers, both of which have about 0.001% of happening.
feel free to bash him all you want, he wont have any solid proof that your doing it, then again, if hes bashing you, personally id let him KNOW that im the one doing it back to him.
PS: if your STILL nervous about it, use a proxy. google "free proxy list" and you should have more than enough (just gotta weed out the non working ones) or take a lunch break to mcdonalds w/ your laptop and use there internet to do your e-bashing.
suggestion: copy his site and report it to google to bump his site off the pages

evil tactic, but fight fire with fire i always say