Well for starters you should always dash before you 5D from a BE combo.
22C only works with two conditions. The first is when the opponent is hit with certain moves, namely 3C and 2D. This trips up the opponent and causes them to go into a state where 22C works. In your case, 5D is not one of these moves. The other condition is that the opponent must touch the ground at least once for you to pick him up. It's the reason why you can't immediately do a 22C from a stray 3C. Though for most BE combos you wouldn't need to worry about it, since 3C > 5D is the way to go into a BE combo.
So if you want to do 22C after a BE combo, you have to make sure to input 3C somewhere in the combo. Other moves can be linked into a 22C, but they're mostly blue/black beat combos so I wouldn't know much at that point.
If you want to hit the opponent with 5B 6A, you have to time your move so that 5B hits the opponent just before he/she hits the ground. If you do 5B too high, 6A's first few active frames will whiff and the opponent will be able to tech after those frames.
A good way to tell if you hit 5B right is when the opponent is at about the same level as Ragna when you hit with 5B.