Hi L...I would like to say right off that I have no expertise in answering your question . I can only relate from my own experiences.
I had two ( of my seven ) children that had problems with speech.
One was a girl, I was in the hospital for a prolonged period of time, the children were being "juggled" between my Mum, my husband's Mum, and my husband who took them home every night.
The little girl had a very bad ear infection that no one knew about, nor was it treated for a long , long time, just as she was learning to speak and sounds were "locked" into her brain in a distorted manner which caused speech problems.
The other was a little boy who suffered a linear skull fracture with massive hematoma when he was six months old. It damaged his speech center.
They both knew people were talking with/at them, but they did not understand what was said. For them it was like being with people speaking an unknown foreign language. The girl, of course came out of it better than the boy.
With him, especially when he was tired, was great difficulty understanding. One thing I did was to put my hands on his shoulders, look him in the eye and gain his complete focus, speak slowly and ennunciate ..this seemed to help greatly. He still has language problems, brilliant boy, they never could accurately estimate his IQ because of his language difficulties but guessed well within the highly superior range. He is 34, still has problems reading but has his own business and does well.
Now, by virtue of being disabled and old, I find myself living with three sons , one of whom has a wife and son. ( Want to interject that I DO NOT SPOIL this child..maybe indulge him a wee bit LOL)
When he was four months old and fussing for things, drinks, food , whatever...I thought to teach him a bit of sign language..he is a bright and clever little boy. I taught him simple signs, drink, milk, food, mum , dad, hot cold, stop , go, tired, play, ect ect. His mom then bought him a baby einstein first signs video. So, the fussing stopped because he could now communicate his wishes. By the time he was six months old he had a "vocabulary" of about sixty signs.
Many people thought it would deter his speech and were very critical..some offensively so. I was a bit apprehensive that they were right.
It turns out they were not right. He will be three on Sunday and he has an extensive spoken vocabulary. It seems the ability to communicate with his sign language gave him a boost of some sort with spoken language. He is a quite a bit ahead of other children his age with his speech.
I did not think of sign language with my own children until they were around eight or ten and it seemed to help them as well as this little boy who has nothing amiss.
In my opinion it is very frustrating for a small child NOT to be able to communicate with others. The sign language gives them a vehicle to express themselves and lessens their stress.
With the two of mine that had actual difficulties it was a great help to them to learn spoken language .
With my grandson , who has nothing wrong, it gave him an advantage to learn spoken language.
My advice would be to try it. Use the words with the signs. I think this is very important as your ultimate goal is the spoken words.
If you dont like how it progresses you can always stop.
BUT if you never try, you will never know if or how much it could help your little boy.
As far as his "delayed" progress please remember that when an average is determined there are also high and lows.
His developement in certain areas may be a bit slow appearing now but he could easily catch up in a couple years.
Dont let him be branded by medicaleese ( how is that for a made up word?)
I had one so severely learning disabled, dislexic ect ect..at five his IQ test was given, he scored between 80 and 200. Keep in mind and IQ is ONLY the size of the bucket that can be filled. A big empty bucket is not to be desired above a smaller filled one.
I was told this boy would never be able even to mainstream in school due to his learning disabilities. I found a way he could learn and taught him , and his speech defective brother, to read.
His junior year of high school he received a letter of commendation from the superintendent, principal and school board and faculty for maintaining honor level grades throughout his high school years.
Kahlil Gibran said that we are limited only by the limits of our imaginations and I really clung to that.
Everyone can learn..one just needs to find the path that a particular child can navigate.
Again, please try the sign language, it may truly be a blessing to you and your little boy.
Please email me if you like.
Wishing you all the best/
God bless
Grandmother Lowell