Each of the things you listed gets you something different. If you want to teach adults or at a university, then don't do Teacher Ready.

The CELTA and Delta are okay, but you're going to probably have to keep working at either public school programs or language schools while you do all of that. Doing a Delta seems like it leads most people into managing language schools.

Doing an online master's or one at a program in Japan might not be that bad of an option. Would you do it part time or take time off from work to study? Do you think you would be able to get a better job than what you have now while you're doing it? What kind of jobs do the people who go through the programs you're looking at get? Anyone who generalizes too much about what you can expect after doing an MA is probably full of shit because a lot of your prospects gained from one are going to be based off of the skills you learn and people you meet. If you go through a shitty program you're going to end up working at a language school being supervised by someone with a Delta. So before doing an MA, I would suggest snooping around and seeing what kind of jobs alumni have. And then evaluate it based off of the curriculum. That is, are you going to be summarizing a bunch of bullshit to get a piece of paper, or are there practical skills that you're going to learn from it (e.g. assessment, corpus, teacher training, etc.).

And these aren't the only three options you have going for you. I thought I was pretty much stuck between choosing the same three things but decided to apply to MA programs in the US that cover tuition and give stipends for teaching assistantships. It's not some cut throat high stakes field. I'm sure you could get some school in the US to pay for you to go there and come out of it with experience teaching at a western university if you can get into one of the programs you mentioned in Japan. I know that moving back to the US isn't for everybody though. I had taught abroad for a long time and was quite apprehensive about it but have no regrets.