Hi Dillon,
In response to #1. I suspect that by going to 3 under you have changed the dynamics of the bow a little. A lower center of pressure on the string will change how the bow feels in the bow hand and where/how it presses into your bow hand. Most find that a considerably higher nocking point on the string helps with this. You might try about 3/4" high.
This change in the pressures MIGHT be making the bow react differently than you are used too and causing the string slap. Since you have watched my videos, "bow hand/ bow arm part one" gives a suggested grip for the bow and a pronated elbow position. Can't really suggest much more with out seeing your shot.
For #2. Yes, the arrow nock is higher on your face so your sight picture has changed and you haven't probably adjusted to it yet. Your arrows will appear to hit lower because you have changed your point on distance and hence your "gaps." This will be true no matter the label you put on your aiming method.
Here are a couple suggestions for your consideration.
First, wear an arm guard as you learn new methods. Simple self preservation -- archery should never HURT! Work on that bow hand grip and bow arm.
Second, with any change, give it enough time to take effect. It WILL NOT/CANNOT happen in one or two practice sessions. You need to stick with the change for 21 practice sessions so if you shoot 3 times a week, that will be about 2 MONTHS!
If you are able to post a video or send me a link to your video, I may be able to help/suggest more.
Good luck with it.
Arne