To the OP. I'll hit a 100 dives this year. Not super experienced as most on SB but my nearly 100 dives are in warm ocean, cold ocean, strong currents, no currents, really really cold lakes, high vis and low to no vis.
1. I am going to solo. But just in dives that are way below my skill set. I will think nothing of going out into the lake out back to 35 feet with no overhead and no entanglement in 15 - 20 foot vis to practice buoyancy, SMB deplyment and other "light skills". So far that's the extent of my solo. Is this really solo or just a bigger swimming pool? I will have the redundancy and well maintained gear. When I'm ready for something more..I'll take the course.
2. I think I make my instabuddies good buddies. I have a lot of instabuddies. Remember, if we have an instabuddy, that makes us an instabuddy. I actually think the biggest reason most instabuddies are not good buddies is because they think that if they lay down the ground rules they will appear less experieced. This is because on all the dive boats, people seem to gear up, shake hands, and get in the water. You will never get the perfect buddy on a boat because we're all here on SB, not on the boat. So what I do is force the topic. I tell my buddy about my gear, my weights, octo etc. and aske them about theirs. I tell him/her what signals I'll be using, and I say that we will stay shoulder to shoulder and check gas every 5 minutes. If they initiate, I will listen, if they don't initiate, I do. I have never been balked at. I think its been appreciated even if I am the less experienced diver. People are shy. Talk to them.
3. Your level of comfort will increase at your own pace, number of dives, training and confidence. There is no magic course that says complete this and you're ready. There is also no magic number of dives. But what I will tell you is that if you are confident that you can solo without a course or at least 100 dives, it could very well be false confidence. Understand the difference. If you don't, then we must start discussing Darwin.