+100 on the vertical stuffer. A minor investment, but totally worth the money.
Charcuterie is a good book to pull ideas from but don't look to it as a step by step recipe guide or you will be sorely dissappointed. (The author was one of my instructors at culinary school). Also, you didn't mention any chilling being done between the first and second grind. My second concern is that you mentioned a mealy, crumbly (?) texture. This could be due to the lack of establishing a "primary bind". This is a key step that many people forget. After you grind the meat, you want to mix it thouroughly. If you are using your Kitchenaid to grind still (eek) throw it in the bowl with the paddle and mix just until it starts to look sticky.
Temperature control is the most important thing that you can do for both your brewing and sausage making! In a commercial kitchen that produces a lot of sausage, the meat grinding equipment is often kept and used right in a walk in cooler. If not, as much of the equipment as possible is kept in the freezer. All the time. This is why I like the old cast iron meat grinders a bit more than the Kitchenaid. Not only do they look cooler but they hold the cold of the freezer for a lot longer!
*forgot to mention the stuffer* it's a good entry level stuffer. You can do a lot with it, it's not terrible to clean, and you cant beat the price. If you're looking for something that's going to last a bit longer keep an eye out for a stuffer with metal gears. The cogs on this stuffer are plastic and if you go crazy (which, lets face it, we all know you will) on the sausage making you'll wear them out after a while.