Please understand that I am not an expert at teaching special needs TCC. While I do have some experience, mostly it has been in teaching seated TCC.
Teaching someone who has one arm is not something I have had the privilege to experience yet, though I would certainly appreciate the chance to do so I would only do it with the understanding, up front, that such an endeavor would be a learning experience for both of us.
Remembering my time learning how to teach seated TCC is why I highly recommend finding a teacher who has experience with that type of teaching already. Because it took me quite some time, and more than a few visits to the "School of Hard Knocks", to learn how to effectively teach seated TCC, I can clearly see that teaching someone with one arm will present some unique challenges. An instructor with experience doing so would certainly be the most helpful for your progress.
However, I clearly recognize that finding a qualified instructor with that type of knowledge and experience will be very difficult. With that in mind, I would recommend finding a teacher who works with a large group of other teachers.
Any teacher of the International Yang Family Tai Chi Chuan Association will be a good bet, as we have the full resources of our worldwide Association of teachers and Masters to draw knowledge from. Yes, I am blowing the Associations horn here. A little.
OK, a lot. This is a very good group of people.
Of course, any large organization of dedicated teachers would be just as good for this purpose as they can also draw on their peers for assistance if/when needed.
If you need assistance locating a school near you, please just let me know where you are and I will be happy to assist you in any way I can. You can email if you'd rather not disclose your location to the world, my email address is: firstname.lastname@example.org
As for the "side effects" question...
My answer is, "Yes, practicing Tai Chi Chuan will cause side effects".
These will include but not be limited to: improved health, vitality and energy.
All of these side effects, and more, will occur if you practice diligently.
You get out of this art what you put into it;
One days practice gets you one days worth of results.
Please do not hesitate to contact me if you'd like help finding a teacher, or for any other questions you may have.
I may not know the answers, but I do have a rather extensive group of Instructors and Masters I can draw from to get them when needed.