The split is caused by injury to the matrix. The acrylics are not applied to the important growth area of the matrix, so it is not the acrylic itself that caused the problem. The only way wearing acrylics could have contributed to the damage is by rough manicuring (for example, heavy filing or vigorous manipulation of the cuticle, etc.). Some women are overly rough on their nails because the acrylic overlay makes them ideal tools.
In general, wearing acrylics doesn’t injure the matrix. Since the damage is to the nail matrix, the split cannot be corrected. The thinness and weakness are probably due to damage to the matrix as well.
You are doing a good job of observing and describing nail plate dynamics. One can only guess at the cause of one side growing faster than the other, but I suspect a decreased blood supply to the matrix that is caused by many minor injuries to the nail bed over time.
Much can be learned by observing the direction the ridge is growing in. The nail usually curves toward the slow growing side. I sometimes inject a cortisone-type suspension into the base of the split nail to reduce scarring and help the nail return to normal. Or, sometimes I’ll use a cortisone injection to slow the fast growth side of a nail. This won’t correct the damage, but it might help even the rate of growth. -Orville J. Stone, M.D.