Delay in work permit processing is affecting my work. How to address the gap in my CV? I am worried about my future prospects
I can't help you with your mental issues about loss of focus, but it would be good to keep in mind that you aren't alone. Everyone else currently studying for a doctorate or in a non-permanent position is in the same mess caused by things completely outside your control or influence. You aren't falling relative to anyone unless you give up. The "gap" will mean very little if anything. People will understand it because they (we) too are living through it. 

What governments do about work permits is also outside your control. Make progress on the things you can control and influence. 

See a counselor if you need to about depression, but be assured that people will take the current worldwide disruption in to account when things settle down. In some ways, you might even think of it as a respite from schedule demands since the delays are inevitable. 

Also, you can't change past decisions. "... would have enabled ..." means nothing at this point. You are where you are. Make a schedule, get some exercise, take a nap, talk to a counselor, consult with your advisor, ... anything. But also relax. If the world ends it won't matter. If it doesn't then you will get back on track along with everyone else. 

Have patience with yourself as with everyone.