Has your little boy got grommets, or did it clear on its own? If grommets, long has he had them? If a while, are they still in or have they fallen out? My DD lost her grommets after about a year, I think, but in her left ear, the hole didn't heal and she was left with a perforated eardrum, which gave her hearing loss.
If he hasn't had any grommets fitted, are you sure the glue ear isn't coming and going? My DD has worse hearing if she has a cold, so even now it fluctuates. It doesn't take much for sound to become muffled, especially at certain frequencies, and sound quality is pretty crucial when you're trying to learn how to talk :-(
Really sorry to hear about how much you're struggling. Can promise you I've been there too and it's so tough, especially when progress feels slow or even backward. I'm not a speech therapist at all and I'm sure there'll be people along soon who know proper stuff. I can only give you my own experience dealing with a child with no language and hope that maybe some of it overlaps with your own situation!
I do think that acquiring language isn't straightforward, and there seems to be a lot of experimenting from the child as they work things out. Some experiments work, others definitely don't, but I think there's some logical process going on in the child's head that makes them try out bizarre ways of saying things.
My own DD refused to differentiate between he/she/her/him/his/hers for the longest time. Not just mixing genders, but also the grammar - ie 'him's coat'. She knew the difference between a boy and a girl but refused point blank to grasp the language aspect. It's only been this past month that she's getting it right MOST of the time, but it's still a weird quirk that pops up in her conversation after nearly 3 years of me modelling the proper words
.
Hoping a therapist pops along shortly for you! xxx