UBPClaw, Thank you for your question and joining the Tees2Greens forum!
Yes you do bring a very unique situation, but the problems and questions are fairly common for your case. I have taught two individuals that were only able to use one arm (the right arm) while hitting the golf ball.
One of the students was born with a very short left arm that never grew correctly and he could not use it all in the golf swing; the other was very similar that he was a very accomplished player that had an accident that took his left hand. Both tragic yes, but the perseverance and love for the game they and you posses should make us all sit back and put things into perspective.
Although these two golfers didn#%92t use their left hand at all in the swing it sounds that you are able to use it as a guide to some degree for stability in getting the club started away on a decent path which is fine, then falling out of the swing through impact and finish. This is all fine, but we really need to concentrate on your strength of your right side and using your body to its fullest potential; if we partner these with the correct fundamentals we will be able to improve our direction and touch.
I would also like to thank for the picture and if possible I know I and everyone else on Tees2Greens would love to see a video of your talent.

First of all I like the set at the top and width that you have created, but as we can see the club face is pointing up to the sky a bit much. This results in a closed club face that can influence the ball to go left and if you are having left trouble, weaker is better. I would like for you and try to get that toe pointed down a bit more at the top and maybe weaken the grip; this will help the club face to not close so much through impact.
In relation to the grip, I found it best to hold the club closer to the bottom of the grip for my students or where it would be normally with a two hand grip. We thought, hey it would be there if I could grip with two hands so why not. It also shortens the club a bit to make the club feel lighter.
As you swing the club through, a lack of activity in the lower body clearing with a shut club face can make the ball go left quick and in my two students this was very prominent. Both had a tendency to concentrate so much on just making contact that they left every other swing fundamental out, throwing the club head at the ball from the top of the swing. I want to see your bigger larger muscles used more to help pull the club into impact so you don#%92t have to feel like you are working so hard to just make contact.
Obviously, I know you are more interested in just contact since you play the game well, but we have to have the thought process not to just hit but to swing.
There is a fantastic one arm (right arm for right handed players) drill to help players be less influenced the left side and learn to clear through with right and keep the arm and body helping each other. It also teaches the correct right wrist set that should remain the same even through impact; I really think this your ticket. I will find it and pass it on.
The arm and body need to move together in unison. If your torso moves too fast, you can loose that unison between hand and body. This can result in an open face producing a slice or shot to the right and the club lagging too far behind. If your torso moves too slowly and your arm to fast on the downswing, you may cast or flip the club through impact with a shut clubface at impact.
It sounds like you have a bit of trouble with your arm swinging to fast and the lower body beginning to be non-existent or not involved enough. So lets work on that lower body getting a bit more active through impact and always remember to get to that full finish into the left side.
I bet you already do so, but it never hurts to always be working out the shoulder, forearm and wrist. I had my students work hard to gain as much strength in those areas so they could be able to stabilize the club in positions anywhere in the swing, meaning wherever they stopped the club during the down swing or backswing to work on a position they could handle the true weight of the club. Controlling the weight is vital and making sure the proper weight of club you use for your situation can mean in control or out.
The club weight will definitely help in the chipping department and I suggest a Cleveland or traditional type wedge with little or no bounce and some good muscle on the back. You will be able to have a club maker drill holes on the back muscle to take weight of the club. You want it as light as possible to gain control for short pitches. You will be able to swing the club easier and hold the right wrist angle through impact better.
On the long irons, I hear ya! They are hard to hit for most players and that is why the Hybrid club came along. Have you ever tried them? I really like that possibility for you to maximize your distance with these clubs. They are easier to hit, get into the air and they give the added distance without having to work any harder. Maybe give them a try, but just be sure the weight is right for you.
I would love to see you swing on film to really help you more and I hope some of these suggestions help. I will look for the one arm swing drill that I have used so many times and either post it here or email you.
Let#%92s be sure to weaken the grip a bit.
Work on getting the club a bit more square at the top, or toe pointing down more.
Get the body working together with the arm more in unison. Not one or the other being over active, timing is vital. I believe this to be the real problem; your arm is out racing your body searching for power by itself on the down swing. Get the body moving!
Work out the wrist, forearm and shoulder. Be able to stabilize the club anywhere in the swing in the correct position. You don#%92t have to over work on the course.
Make sure the clubs are right for you. Off the rack wont do for you, you have to get as much weight out until they are comfortable to swing. If you must go custom then do it; will only improve your accuracy and feel.
Again, I hope this has helped and get your video to me!