Re: Producer wants to buy my song: do I still get royalties?
The facts that you have presented do not quite add up. The producer of the live show would not be buying your songs, he should be licensing them. More importantly, he should be licensing your songs, and all other songs performed, from either ASCAP, BMI or SESAC, the three performing rights groups. You should join one of these if you intend to continue your career as a songwriter.
The real question is if the performances are being recorded and then later sold. This is a much more complicated scenario. It is governed in part by statutes which grant you a mechanical royalty of $0.08 for each copy of the song reproduced. However, this statutory rate is a default rate that is paid if the rights are not acquired via negotiation. The general practice is to pay ¾ of the statutory rate.
You should not, under any circumstances, sell your song. You do not have to. You should be licensing the material. But this is generally done with either the band or the record company that wants to use the material. This is why I am confused by your statement that the producer of the show wants to license the material. Is this a broadcast situation (which is different from a live show, but is still subject to ASCAP, BMI or SESAC jurisdiction)? If so, then the analysis changes.
It sounds like you need to contact an attorney. You are dealing with one of the more complicated aspects of the copyright laws, one that even attorneys do not always get right. Thus, you should seek out an experienced professional to assist you.