JammyK you could be me. My DD has just turned two and her speech is delayed. I feel exactly the same as you about playgroups etc, honestly, i could have posted all of your posts for you. Some of the mothers have even blatantly asked me how old she is and then go quiet when i say how old she is, i even had someone making underhanded bitchy comments once that made me stop attending a certain play group i was so upset.
I have to say, i think your HV is being dismissive and unhelpful and i think you would benifit from a second opinion. Don't be fobbed off with he is probably a late talker either, it probably is the case but you need to have this confirmed for your own peace of mind and also how you go forward with ideas helping him to talk. I have had, and still do on and off, all the same fears re DD as you have had about your son. My HV was fantastic when i raised my concerns at 18m and arranged for a refferal to a peadiatrician withing a month (how good was that!), also a speech therapist. The peadiatrician was able to put my mind at rest regarding my biggest fear (autism) and said she is too, advanced in other areas. You mention in your post that your DS points and that is really positive, the health professionals always question regarding this and it is a good sign, apparently.
My DD was seen at home by a SALT and has had a course of group speech therapy, i have to say that at the sessions she is as quiet as a church mouse and does not say a word, but i think it has really helped her. She is starting to say new words every week now although not one of them is clear, ie, she never finishes the words.
This is some of the advice that i have found really useful.
Choices: offer DS choices, such as, would you like milk or juice. Is that a cat or a dog. Repition: it drives me nuts but i repeat repeat repeat - would you like milk or juice? DD will say ju ju, oh, lucy would like juice, juice lucy is having juice. mmmm juice etc etc. I thought it was ridiculous, but believe me, it works.
Take the pressure off: dont ask your DS to name something unless you are sure he is confident with the word, rather give him a CHOICE again, is it a bus or a rabbit, that way you are reminding him of the word and he will feel good for being able to repeat it.
Dont ask questions, i am really really bad at this, my SALT said she would slap my wrist every time she heard me say, oooh look lucy, have you got a XYZ. That way, all she was ever saying was yes or no.
Role play too, tea sets are amazing. Another thing they do at the group is playing with puzzles where you put the shape into a space, you knwo the sort, but the shapes are kept in a bag and the children have to take turns in fetching one out of the bag and trying to name the item, so will be asked, is that a train or a house etc etc. Apparently turn taking is really important part of language development.
I started doing all these things with DD and nearly gave up, thought i was wasting my time as didnt seem to be working, then all of a sudden she was using words i had offered her when doing all of the above. She still has what i think is significant delay and i have actually asked for a further referral but doc told me to watch and wait, which i actually think is sensible, is said ok, provided she promised she would refer if i got worried in near future, so we have agreed to leave it at that. But the SALT has really worked, even if the problem, which i suspect it IS , is just htat she is a late starter, it has been of great benefit and i am in the system should a deeper problem manifest itself.
I hope my ideas help, i thought i was doing all the right stuff regarding talking to DD, but little things in HOW we talk to our children do make a difffence.
Dont beat yourself up over this, i often think, oh i wish she could talk, but she is who she is and i dont want her anyother way than who she is, cos she is blardy lovely so she is. Please don't let dd pick up on your anxiety, you did say in one of your posts "i'm sure he could speak if he tried" and i think you should be thinking "i know he will speak when he is READY", that way the pressue is off both of you. I have to say though that other mothers at play group etc can often make you feel really shit. MNet mums are lovely though