How can I file my I-526 petition before I invest the total $1 million direct EB-5 investment?

Probably not. Being "in the process of investing" still needs funds at risk ("To qualify as an investment, the immigrant investor must actually place his or her capital at risk. The mere intent to invest is not sufficient.")

You can file if you clearly show a commitment/intent to invest and fund the remaining amount within a year as you have described. We work with investors in similar situations all the time who can''t fully fund at the time of filing for a variety of reasons (in process of selling home, unvested stock options, etc.) and have gotten those cases approved.

No, they want to see the money committed.

Yes, it is. Your attorney will guide you in this process and the collection of proper documents.

Technically, you can make the argument that you are "in the process of investing." However, your case will be very heavily scrutinized. It is not worth the risks in my opinion, given how long it takes to get an I-526 approval and that the case needs to be approvable when filed.

These cases take over two years to adjudicate. If you are ready to have to refile, then you can try and show the money is identified. They have allowed some cases where less than the full amount is invested but generally only where the money is identified and the investor can show they are in the process of transferring but for example, cannot do so because of currency restrictions. If you can invest the full amount prior to filing, that is the correct way to do it.