Certainly, if you can avail yourself of the opinions of an attorney at little or no cost, go ahead. You complied with the DMCA as far as removing the file when notified. His recourse is to sue you, by VOLUNTEERING information or funds you only diminish your standing should it come to that. His material is freely available on other sites anyway, and they will not be as understanding as you were to take it down. Regardless of how much you enjoyed the book, I would cease communication with him as he has chosen an adversarial position. Anything you say WILL be used against you, you can rest assured.
Besides the initial phone call and an email apologizing for him having to waste his time on the matter there has been no further contact. I am working on retaining counsel to do the talking for me. Your advice is solid. Thanks.