There's nothing wrong with crabbing. It's a useful pilot skill to have when you need to make a steep approach or just find that you've come in too high to make the runway. I think the point the others guys were making, certainly the point I would have made, was that trying to crab with a mix is the wrong way to do it. Absolutely it will be good for your flying to learn to crab with your thumbs, especially with the flying site you are using. As for your CG, there is absolutely no way we can tell you how far to move it back. The best thing to do is measure where it is now and calculate it's location relative to the mean aerodynamic chord. The normal range is between 25%-28%. A few scale planes like to be more forward than that, and a few 3D pilots will go back as far as 30%. I'll bet you'll find based on your descriptions that the CG is up around 25%, so moving back to 27% should improve the flying characteristics all around and give you enough elevator authority to flare properly for landing.