You seem to be depressed with the complexity of the problems you are facing. If you believe in what I advice, I would rather suggest you to relax in the first instance. With the every bit of stress
you undergo the problems get worsened. Just because of your stress the acidity increases leading to the tightness in the throat.
What does the endoscopy
Gaestroenterologist will not do a biopsy
unless it is indicated, so do not worry about that. Regarding other problems in the throat the sensation of the sticky mucous in the throat is because of the inflammation in the throat giving you the false sense of presence of mucous. That is why you are not able to bring it out.
About your breathing difficulty, you need to consult a good chest physician/ a pulmonologist for a complete check up.
Please keep me informed, do not get depressed, do some relaxation exercises and drink plenty of warm water. Any more doubts you are welcome.
Dr. Naveen Kumar