Hi deborahdreamer. I couldn't really see anything in the progressed chart - one degree orbs are normally the widest considered for progressions. Also, while the progressions may have reflected some elements of your experience at, and around, the birth of your Son, the transits would have probably done this in more detail, and furthermore those transits are still with you because your son embodied them in his being when he was born. In other words they are always in the synastry you experience around him. So I'll just focus on the transits/his birth chart as they seem to me to contact your chart. This won't be a systematic look at anything of course, but just what happens to jump out at me.
Two things immediately jump out at me. One is the conjunction of transiting Pluto to the 3rd house Sagittarian Venus. The other is the conjunction of transiting Chiron to the Sun Mercury conjunction in Capricorn in the 3rd, with transiting Saturn opposite all three, and transiting Sun just 2 degrees separating from squaring the opposition of transiting Saturn and transiting Chiron.
Your exact natal opposition between Moon in Scorpio and Chiron in the 8th house perhaps reflects something of your experiences as a Mother, but I'll stay with the transits/synastry because that is closer to what you asked in you post.
Your son's T-square aspecting your Sun Mercury conjunction suggests to me that he is going to teach you a very great deal about that part of yourself. By way of an attempt to summarise the essence of that natal conjunction, I would say that there is a need to find your vital self through alignment with the correct 'law' - a sense that you wholeheartedly embrace whatever you deem to be the appropriate and necessary way of going about things. The law of your own integrity is your goal and it could be that with the birth of your autistic son, transiting Saturn and Chiron somehow forced you to profoundly reconsider your loyalty to the reality from which you had previously operated.
With Mercury conjunct the Sun here, there is a sense that perhaps your goals and values are characterised by the development of mental dexterity. This part of your chart that is particularly strongly activated by your son could be seen as symbolising the Self and mind trapped within a reality - and as transiting Saturn and Chiron contacted your Capricorn conjunction, this manifested in your life through your son's arrival.
I don't know if you already know this but Saturn and Chiron are both associated with wounds, and the processes of living with, and working on, those wounds. One could read the transits to your Sun Mercury as illuminating what in this part of you needs to be examined and healed (Saturn), or if not healed then understood and accepted (Chiron).
I feel like I'm disoriented and struggling to maintain a coherent line of thought here, which might be synchronous with your experiences as the mother of your autistic son.
I suppose basically what I'm trying to say is that the more you can learn about and reflect upon your Sun Mercury conjunction in Capricorn, the more your relationship with your son will become even more a place of flourishing for you both than I'm sure it already is.
And then there's your 3rd house Venus in Sagittarius.
Something that is just occurring to me is that Saturn and Pluto have a great need to be in control when they feel threatened. Therefore, your expressions of your Sun Mercury and Venus have probably had to be curtailed to suit the sensitivities of your son. And a profound understanding of what is truly worth-while and meaningful in life may be gradually arising through this.
Venus in Sagittarius in the 3rd house would ideally like to be exploring much of the time - free to pursue the delights of the realms of knowledge and understanding. But this part of you may trigger an intense reaction from your son, because Pluto symbolises the primal survival instincts. So in this sense your son has great power over your love of knowledge and he is perhaps forcing you to delve deeply into this part of yourself to see what lies at the root of it, since it cannot merely be expressed on a whim and satisfied simply and easily. Venus is particularly important in your chart because it rules your Libra Ascendant.
I've just also noticed that your Sun Mercury are square Jupiter Saturn in your natal chart, which I feel is also very relevant to what you will meet through various parts of your life, including your relationship with your son (whose Sun Saturn Chiron t-square of course aspects this whole Sun Mercury Jupiter Saturn configuration of yours). This configuration I feel should be the starting point in looking at what can blossom in you through your relationship with your son. You might also want to look into how it is generally for people when their Saturns are in square like they are with you and your son - this could be the pivotal contact between you.
If any of this is helpful and you'd like to ask anything else then please feel free. I really feel that your post is a perfect example of trying to make the best possible use of astrology.