Don s. You are measuring draw length correctly. Throat of the nock to the deepest part of the riser, plus 1 3/4 inches. That's the AMO way and the way most most bowyers do it. However, you'll also get pretty close by measuring to the back of the bow. Most risers are from 1 5/8 to 2 inches deep, so measuring to the back of the riser will yield very similar results.
In addition to physical size, where you anchor on your face. how much bend you put in your bow arm, whether you shoot high or low wrist, whether you lean into the shot and/or bend your head toward the bow string at full draw all affect your draw length. Standing straighter, keeping your head more erect, straightening your bow arm, anchoring further back on your face and shooting high wrist will all add to your draw length.
But if you're comfortable shooting now and you hit what you shoot at, why change anything.
To answer your question about ordering bows. Most mid-weight bows gain about 2 1/2# of draw weight for every inch drawn beyond 28 inches, and loose about the same amount for every inch below 28 inches. Thus, if you wanted to buy a bow off the shelf that was 45# at your draw length, you would look for one marked 50#@28. If you have one made for you, you can specify whether you want the bowyer to state the draw weight at whatever draw length you want. A few bowyers actually change the composition of the limb materials to optimize performance at a shorter length, say 26 inches. But most just build the same bow they always build and mark the draw weight at 26 inches.
Being 6' 1" and drawing 26 inches is no more unusual than being 5'10 inches and drawing 29-30 inches. Different strokes for different folks. Good luck.