Thanks for playing despite the nightmares! The antimatter should appear around 2% of the time, so I think you were just unlucky.
I encountered that bug during testing but thought I had solved it, there must be some edge case that I missed. Thanks for letting me know, I'll look into it!
That's a good suggestion, I like the idea of giving some extra statistics about the game other than the score! There's software for generating chemical names from structures so naming them should be possible, but I would need to do some more research before trying to implement it myself; reducing them to names would make tracking statistics on which molecules you made easier too!