Unable to remove old/dead devices from iTunes device sync list.

I've been an Apple user for decades. I have many MANY apple devices, even going back to some of the first gen hardware. I'm attempting to synch my iTunes to one of my MacBook Airs. I cannot do so because I've reached the limit on devices. I went to the device list to remove ones I no longer use from synching and there were 4 that were grayed out. I wanted to remove them but cannot do so unless I can sign in with them, and some of them are inoperable/unbootable. It might seem like I'm a wee bit of an Apple fanatic but right now I can see 15 Apple devices in sight in my office and that's not nearly all that I have. Now comes the strange part. For the last few hours the number of grayed out devices has increased dramatically, now it's up to SEVEN out the eleven. Is there any way to remove devices from my account (for syncing music) f they are unusable and cannot boot anymore?