Maybe go SIC for a 135 company to get some experience and get some more confidence.....the standards are typically "way lower" because you are just trying to meet the SIC standards/insurance requirements. Example: minimal automation knowledge required (depending on the particular aircraft) as well as no steep turns, no single engine missed, etc. on the SIC checkride. Just a thought and my recommendation for sure.....especially if you have had trouble in the past with a structured 121 program......go get some experience, the airlines aren't going anywhere.