When suicidal thoughts surface, it's natural to isolate. It's the same as being told you have a few years to live. You don't want anyone to care. It makes it easier to let go if no one's around. You got to fight that with everything you have, with every fiber of your being. Fight like you never have before. You'll get tired and want to give up but you'll find it might ease over time. You can't blame yourself for your depression and suicidal ideation. Could you blame a heart attack victim for having to go to the hospital and need surgery/medication? Make it up to your wife in the ways that will mean more to her. Take her on a date, spend as much time with your kids as you can (even if you can't be 100% there mentally). Take it from a woman, we hold actions higher than words. That being said, every time you feel like saying 'sorry' to her, tell her you love her instead. It positively shows that you appreciate her instead of just feeling guilty, which will make her feel guilty for you feeling guilty.
This is my experience from the opposite side of the spectrum, anyway. Good luck, sir. Hang in there.