Almost there, but needs a little cleaning up. I would change the "how to" to products or ordering information. Something like that. Get rid of "the" on the collar names. Get rid of "footer" at the bottom of the page. Consider accepting Paypal.
A machine that is capable of sewing sheath thickness leathers needs a machine that has a "walking foot". These are industrial machines with external motors. The one you pictured has a very small motor, and will burn out in no time, It will also give you a poor quality stitch.
Pig: Garments, purses, footballs, etc.
Lamb: Garments, and garment liners.
Snake: Belts, shoes
Horse: Holsters, belts.
You should already know latigo is good for collars and tack.
You can glue the pieces together with contact cement. I The use the kind sold by Tandy Leathers. Are you using a stitching horse? What type needles are you using, harness, glovers? Are you using a diamond awl to punch holes? Yes they need to be sharp just like a knife does.
Vinigaroon has already been mentioned. Here are a couple more: tobacco plug soaked in amonia and walnut hulls. Make darn sure you wear rubber gloves, especially with the walnut or you will wear it on your hands for about six weeks! Both are excellent stains, as is vinigaroon.
Some of the thread is okay, but only for hand sewing. I am having to really look at the thread as I pull it off the spool as I find a defect every five yards or so. I don't know how it is (quality) further down the spool. I also have to give it a tug test before I use it. I was disappointed too.