Welcome!
I technically started dancing 2 years ago, but had to stop and start many times due to medical stuff. I think that if you add it all up, I have about 14/15 months of dancing in my body.
Right off the bat: Don't let anything you are feeling right now get to you
too much. It typically takes 2-3 years to get through and come out the far side of lessons, become a regular at a milonga, and
possibly find a longer-term private dance coach, before you even start to feel at home. Some people do get there sooner . . . but some people get there later, too, and my personal experience with "medical stuff" is that it puts you in the "get there later" group, especially if you're past 40 years old.
I've learned quite a few moves but I struggle to connect them.
What I'm about to say is not universally agreed upon, but here goes:
Tango isn't about moves. It is about walking to the music with another person. Learning some steps can make that more interesting, but ultimately, everything is improvised in the moment.
Everything.
You can learn to improvise better by focusing on cleaning up "movement particles" such as single walking steps (forward, side, back), pivots (both directions), rocks (in place and turning), and various changes of axis (on/off), embrace (opening and closing), and level (more/less knee bend). Clean it all up on both legs, and in both systems (parallel and cross). Then no matter where you end up relative to your partner, in the music, or in a crowd, you can follow up with something. This is how you link movements into a smooth flow that matches the music.
There are a ton of tips and tricks to improve the linking itself: See the entire musical phrase as a wave that goes from A to B in space and time, and think more about the wave than about the individual movements that make it up. Push into movements to find enough energy to carry you through that wave. Learn that every "mistake" is an opportunity, and that if you keep going through and after it like you meant to do it, you won't freeze up. "Listen" with your body to what your partner is doing or wants to do, and go with their proposals sometimes instead of trying to choreograph the whole dance yourself. Use pauses to feel the musical phrases, prepare your wave of energy, and listen to your partner.
And so on for 100 years.
All of that stuff is advanced relative to what's taught in the first couple of years of group classes. I'm not saying it's easy. I
am saying that focusing on that instead of on patterns will take you further, faster in your dance journey. I've seen (and taught) some pattern-locked dancers, and they might have 20-30 years of "moves," but they don't dance fluidly. They stutter and halt, trying to think of the next thing. They aren't writing poetry, but cutting and pasting stock phrases from a mental library.
My biggest problem was and always is musicality. Since a lot of my brainspace is taken up by ensuring my steps are right, i dont have much bandwidth left to 'think of' and then execute a muscially appropriate movement.
Focusing on particles, links, and energetic flow rather than steps frees up that brainspace. You aren't thinking about steps any more. You're just doing whatever makes sense in that instant. "I'm on this foot, relative to my partner in this position, with this momentum, so there are only so many ways I can transfer weight or check the momentum while staying with my partner . . . but they're all good. I'll walk here or pivot like this, because it makes sense in this instant, and not worry about what the dance step is called."
Can somebody please tell me how a leader 'decides' on which move to do?
See above. You have a musical phrase. You push off and launch yourself into it. That gives you a certain energy, which you then use to walk, pivot, rock, whatever else you want to do. Doing that puts you and your partner in a certain relative position and system, with a certain momentum. Those things make some follow-up movements easy, some tricky, and some impossible. You mostly choose the easy ones, with the occasional tricky one for emphasis or drama, and that's that.
I imagine a veteran dance has many many sequences in mind
Speaking for myself and many people I know: not really. Sequences, patterns, whatever you call them . . . they are teaching tools. They illustrate how walks, pivots, and so on work, and propose ways to string them together. They absolutely do have names, and to ensure clear communication in discussions like this one and in person, people talk about their dance with those names, but don't let that fool you: Most good dancers move from point in space and time to point in space and time with whatever feels right, and don't care (much) if it matches some pattern, or what that pattern's name is.
Early on, sequences are useful "cheats" to compensate for lack of experience with this way of dancing. But it's important to see past that, and not to let them become a
crutch. If they become a crutch, then whether you've been dancing for 14 months or 14 years, you'll still freeze up trying to match sequences to the real world, where the music has the wrong feeling or number of notes for what you want to do, where your partner's interpretation throws a wrench into what you want to do, and where other couples on the floor block what you want to do.
The lessons that really matter are in basic technique – posture, axis, embrace, how to walk well, how to pivot well, how to navigate the floor, etc. – and not in patterns. Inasmuch as you might want lessons in "moves," they're usually more about how to apply technique in specific circumstances: a sacada is just a walk with a goal in mind, an enrosque is just a pivot with another goal in mind, and so on. These classes are useful for solving more in-the-moment problems with improvisation.
Also, could somebody tell me what the numbers are like where they dance? I had always thought there would be more followers than leaders, but we actually seem to have more leaders than followers, which is a small bit bothersome. Are ladies not as inclined to dancing as once they were? We have some dancers, particularly men from the LGBTQ community, who are happy to follow as well when we are short, which helps the numbers, but overall I'm a little surprised that we are having this problem. Is it common?
This is totally regional, so there's no "normal." Where I live – a North American city of c. 4 million people, with close to 10 full-time dance studios and one or more milongas every night of the week – we are follower-heavy. Sure, I've seen leader-heaving
evenings, but they're remarkable one-offs. Most events here have anywhere from 3 followers to 2 leaders to 2 followers to 1 leader, and it isn't rare for there to be 3 or even 4 followers to 1 leader.