There is no ‘normal’ in terms of sexual history. We all have one. Our history is normal for us.
As to your relationship and your question, I think you have the cart before the horse. Focus on how to repair your current relationship. You need to be completely committed to this goal (if that’s what you want). If you’re hedging your bets and also looking to ‘what would life be like if I wasn’t married’, you’re not giving your marriage a fair shot.
Should the worst happen and your marriage ends, take time before you seek another sexual relationship. As @janbb said, separation and divorce are gut-wrenching and heartbreaking. While it might seem like the easiest solution now, when you find yourself standing on that side of the fence and dealing with the fallout from a broken marriage, if you have a heart, things will not be wonderful for a while.
Many people leave one relationship and jump straight into another. In my opinion, a better idea is to spend some time figuring out what went wrong. Seek some counselling now to help you with the problems in your relationship. If things don’t work out, that counsellor can also help you to learn from your mistakes so you don’t take them into your next relationship.
If you end up single, when you are ready to embark on a new relationship, I doubt very much your new partner will judge you for your past sexual history. Focus on finding someone who is right for you, rather than worrying about whether you measure up to some imaginary norm.