Welcome! Great Intro! Your boy his handsome
Maybe I'm a lil partial to black dogs though
I too have an allergy dog (Curly, in my Avitar). It's been a long bumpy road finding what works, and I'm glad to hear you are doing what you can to help him. There are many threads in the Health section relating to this, so please go through there for ideas, questions, and anything you can contribute to help others.
As for the leash question regarding fetch... What I do with Curly, since she has a high prey drive, will dart, etc, is I got a 50 ft horse lunge line. It's plenty long enough to play with her on, especially with my girly throwing skills
She doesn't mind it, or notice the leash really because she is so ball obsessed. I could probably very easily play fetch with her off leash due to her focus on the ball being so obsessive, but I'd rather not take the chance of her prey drive/ADD kicking in...beside, she's not good with some dogs now that she's gotten older. She's kind of dog selective.