Welcome...I like your project photos....How lucky you are coming across the leather tools. You saved alot of money. I think you are doing well in your tooling for no longer than you have tooled. I think the metalsmith/jeweler/artist will help you become even better.
Sounds like the plan was good right up to the glueing. You can't get it tight because it's stiff? I would try wetting only the back. I only make solo seats so I only deal with a top and bottom. Post some photos...maybe someone else has a suggestion.
Maybe because Mop n Glow is for floors! I know in other threads it's been talked about in several posts of people using it. I use Leather Balm also. I think I'll stick with products for leather.
I don't make whippets or leads but several people on here are excellent at their braiding skills. Maybe they can chime in. I have heard though the lace SHOULD be beveled. It's nice that you have plenty of kangaroo in your area. I love using kangaroo lace!