One more opinion: your offer is more than fair. At an estate auction or yard sale this stuff would not bring anything close to that. Unless you have an immediate use for the various chemicals it makes sense to leave them behind. If you are way out in the boonies and will never again see a LF enlarger, then maybe this is the deal to pursue. If you are near civilization and he will not entertain your offer then I would just walk away. Final two cents worth: all of those glittering treasures, that 'incidental stuff', has an alarming way of turning into plain old photo junk on the way home to show the wife what you bought!
Good luck with it.