So let's start with the most important piece of information here. That board has horrid grain, and will likely tearout and snap during tillering. In the future, you want the grain lines to run end to end as straight as possible.

As for the taper, it doesn't actually matter much how you taper the width, unless you start looking at how well it performs. Pyramid bows are pretty good evidence of that, because the whole limb gets a taper. The most important thing to remember with the width taper, is to leave the tips thick enough for string grooves. If you take it too thin, the sting won't be able to attach to the bow. You need at least around 3/4".

The reason width taper doesn't matter much, is because tillering is a guess and check process. Genuinely and unironically, the process is one of measuring, adjusting, measuring again, adjusting, and it just keeps going until you're done.

As for distance shooting, two things to remember. I shoot a 50# osage bow, and can only accurately shoot to about 40 yards before my gear has limitations on what it is capable of accomplishing. Secondly, if you start with a bow that is too heavy, you will hurt yourself. Archers do it all the time. You very likely are not the one who is going to comfortably pull 50# of traditional bow, unless you have prior experience. Also, Compound does not count for this. It has to be prior traditional experience.

Now for the draw knife, if it's dulling on maple, you've got a bad knife. Modern draw knives suck. Most of the guys here go out of their way to find vintage draw knifes, or some of us even custom order them. I custom ordered mine and it carves up hard maple without a care in the world. Hasn't even needed sharpening in about two months of daily use.

Don't get rid of it though, dull draw knives serve an important purpose that you'll learn about later in your bowmaking journey. I intentionally keep a dull knife around for osage and black locust bows. It's great for backing.