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.

Counting the seven clean days and immersing in the mikveh are distinct mitzvot. There is usually no break between them, but halacha does allow for one when necessary.

You are correct that you cannot immerse before your quarantine period finishes, but it’s important for you to finish your seven clean days as planned, even though you won’t be able to immerse right after you finish them.

Between completing your count and immersion, no further bedikot are necessary, and you should switch to colored undergarments. On the night immediately after the quarantine period finishes, you can immerse.