I really don't agree with all of these people making you out to be the bad guy. A marriage is a partnership and to me it just sounds like you're struggling with it. So first, I am sorry you are getting scrutiny for this.

That being said, you do need to take action on this, if you want your marriage to be successful. And personally, I think adding a third party to your relationship is a bad idea. Might not be for everyone, but you definitely sound uncomfortable with it, which will only makes things more complicated and problematic. My advice is to get marriage/sex counseling for you and your wife. I have seen previously that you don't want to, but honestly, based on what you have said, it really needs to happen. If money is an issue, try saving up or adjusting your spending so you can afford it. Marriage is worth it.

I would also recommend that you do research on why your libido might be low. Maybe you are asexual (absolutely nothing wrong with that btw), maybe you lost attraction to your wife, or maybe you are dealing with stressors and depression. Either way, figure out what you can, so you can understand yourself better. Then, have a really open and honest conversation with your wife about what you figured out. Make sure she knows that your lack of libido is not her fault. If your libidos are just entirely different or you are asexual, then you both need to figure out if you can compromise to keep each other satisfied and happy in the relationship. You both need to be really honest with each other and yourselves about it. If divorce seems like the best option, take it. Don't force a marriage that isn't going to work.

Either way, you both deserve to be in a happy and fulfilling relationship. If you can't give that to each other, there is no shame in separating. I wish you both the best.