You need power. It doesn't take much, but more than your PC puts out. Bluetooth amp suggestion will work, powered speakers will work. I'm a fan of vintage audio gear, available pretty cheap just about everywhere now, and a dedicated system.
I always offer drinks or maybe donuts for a bigger job. If it's just a couple of hours or a half day, probably not. Crews have typically been surprised when I offer, and appreciative. I see it as not just kindness, but also a good practice to get the best possible work.
Communication is key. Clear agreement and understanding up front. Maybe he decided he'd never get the job and he may as well shoot his shot for $1000, but it seems pretty likely to burn the relationship.
I like the new windows! We finally finished swapping ours a couple of years ago, makes a big difference in sound and quality feel of the house, besides the weathertightness. Painting windows became a chore, too.
I am partial to the Porsches! I also assume the tools are based on sponsorship, but it seems like it would be a difficult transition if, say, tool sponsor changes every year or two. I guess they are used to making big changes in a hurry, but changing tools would slow everything down for a...