Oh Mini, he sounds so special! :) I bet he is just adorable. Jack is my first dog, and so I have a bit of a Collie-bias!
By lead-work I just mean training him to walk well on the lead. I hope to dedicate more time to this soon and perhaps have my Jack settling down on the lead a little (hope it isn't too little too late!)
I have never used a half-check, but lankeela's advice is usually spot-on! And she is definitely right about dedicating walk time specifically to training your Jack up on the lead. Much easier, and that way he will definitely "get" it: you will know what you're out for, and so will he, so it'll be more consistent.
We had so much to learn. I know I am probably preaching to the converted anyway, but Collies are pretty sensitive; you sound like you really adore your Jack-treat him with kindness and respect, and never be harsh, or unpredictable in your mood, and you will just have the most special relationship with him! My Jack just likes to be liked, and Collies learn best with praise, encouragement, and fuss!
Don't want to go on any more (!) so my last point is that you make sure training never stops: it's lifelong! There's so much that Collies can do; investing in some puzzle-type toys, like treat balls that Jack has to work out how to open, or the Nina Ottosson wooden puzzle toys, is well worth it to keep Jack busy! Their minds never stop, it's exhausting but so rewarding!
Are all dog owners mad? In the nicest way ever :) x