1. I don't think that they are gonna sell Bitcoin. But I'd love to see how the market and community would react to that.
2. I think the price would drop significantly, the biggest BTC bull is selling his BTC, imagine that.
3. Not really, I was DCAing when it was cheaper, but now I just switched to altcoins.
They create a financial model that allow MicroStrategy investors to get profit without need to force MicroStrategy to sell their bitcoins.
Since September 2020, this model has worked well for MicroStrategy and their investors. This working model is reflected on price of their stock $MSTR that grows from around $150 to $1,500 today.
https://www.google.com/finance/quote/MSTR:NASDAQI see their model works but I am not certainly that they will never sell their bitcoins.