You are definitely facing a number of challenges, and these questions only begin to touch on them. Our hearts go out to you, and we are here to assist you in any way possible.

Your dedication to immersing on time is extraordinary, and it’s clear from what you wrote how important it is to you to immerse on time.

The halachic ruling in this case, though, is that you must delay immersion.

The instructions of Israel’s Ministry of Health are very clear: You may not exit quarantine at all, and that definitely includes going to places like the mikveh, where you might endanger other women if it turns out you are carrying the virus. These instructions also have halachic implications, because not endangering the lives of others is a halachic obligation.

Immersing in the sea is halachically complicated, even though there are cases when it is the correct halachic solution (for example, in locations that are not within reasonable distance of a mikveh). In this case, it is off the table, since you are forbidden to leave your home. Even if there were a way for you to reach the sea without any contact with others, it would likely be in an area in which entering the water is dangerous, which itself raises halachic issues for immersion.

It is truly praiseworthy that you have never had to postpone mikveh immersion. In this case, however, halacha requires you to take a different course, and that will be no less praiseworthy. Please note that you should finish your seven clean days as planned. After completing the clean days, you need not perform any more bedikot, and should switch to colored undergarments.