Fair warning before you read this, this will not be a pleasant read. You have a bad situation. It is best to face that.
I don't see anything in your question that would lead me to want to interview you for any job. You are out of date in your field (and I think most jobs in Physics require that PhD that you appear to have dropped out of) and it sounds as if the most pertinent work experience you have is as a clerk. And you had some type of medical problem that made that job go away too. And you don't even appear to know what field you want to work in.
Your problem is that you are basically entry-level and you are too old for entry level. You are 11 years past your Master's degree (I am making the assumption from what you wrote that you did not finish the PhD.) and have no accomplishments to show for it. You don't have a 4 year gap, you have an 11 year gap. This is not something most employers are going to find impressive. You are well past the "just graduated from college" age and you have no work experience so no proof that you can do a job or will be able to stick out past the first problem (and all jobs eventually have problems). Your competition for every job will be people who are graduating this year and they will have the edge on you virtually 100% of the time.
I'm sorry if this sounds harsh, but the work world is harsh.
I think your personal best bet is to make your own job by starting a business. As a business owner, no one is going to ask about or are about the gap, all they care about is if you can deliver the promised product or service. Start thinking about what kind of a business you could run and then talk to the good folks at the Small Business Administration (if you are in the US) about how to put together a business plan and how to get funding etc.
If you choose to continue to look for an employer instead, you need to treat that job search as your full-time job. You need to spend at least 40 hours a week at it. You will probably need to spend months at it and make hundreds of applications and likely the job you find will not be a very good one because you don't have anything that the better employers will want. (I know this is a bitter pill for someone who got accepted at a prestigious university.) If you get that job, then you need, above all else, to stick it out for at least a year and preferably longer. With your history, you simply can't afford a short-term job no matter how bad the job you get is.