Sounds like my boat looks a lot like yours! My 2 1/2 year old son has had a speech therapist see him for an hour a week, since mid August. He has "Final Consonant Deletion" which means he does not end his words unless it is a vowel sound like "Baby." His therapist has said over and over to not ask him to say words because it's asking him to do something he can not do, and he knows that. She has encouraged me to use modeling like when he says "Duh" for "Duck" I should say, "Yes, I see a duck!" and say the "K" sound slightly louder. After doing this A LOT, he is "talking" more, or trying to.
I think at this point, it is most frustrating for us both when he can't convey his wants and needs. I see him making progress, but SLOWLY! I have told the therapist my concerns that he doesn't seem to be progressing very quickly, and she reminds me that it is like making a sturdy building. We have to place the foundation and then put it together, piece by piece. I believe that he really has the potential but we just have to get it all put together.
I guess a good question would be does your son understand what you say? If he can't, I think that is an indication of a processing problem. If he can follow a direction, that means he just can not articulate what he wants. THAT'S a good thing! That means there is no other reason for him NOT to be able to use language. If you don't feel like you are getting anywhere with your therapist, or that there may be tother things going on, you may want to contact the agency that is providing services for further testing at least. When my son was first diagnosed with a speech delay I also had a Developmental Therapist evaluate him to be sure there is nothing else going on.
BTW, I am also a teacher for Deaf and Hard of Hearing kids, and REALLY felt like I should know how to "Fix" my son's problems. With everything I learned in college, I still don't know how to make this stop happening! THAT is frustrating! I really can understand where you are coming from and believe you are doing what your child needs! Early intervention is where it MUST start!
Feel free to contact me anytime to vent! I am in the same boat!