How long does the EB-5 capital need to be at risk and when can I withdraw funds without jeopardizing the immigration process??

EB-5 funds must be sustained at risk during your conditional permanent residence period (2-year green card) and depending on your underlying contractual obligations (subscription agreement) with a Regional Center, which is a state contract law issue separate from the immigration law requirements. Safe approach would be to sustain capital until your I-829 is filed at the end of your conditional residence period, assuming the requisite jobs have been created as shown in the I-829 filing.

The end of "sustainment period" which is your conditional residence period. In other words, the milestones are immigration process-related, not calendar days/years-related.

Current USCIS policy states that the relevant "sustainment period," i.e., the period of time during which the invested funds must remain "at risk" as the two-year conditional green card period of the investor. Assuming jobs have been created, it would be safe to receive a return of your investment after the two-year green card period has ended and your I-829 is pending.

Funds must be sustained through the 2 year conditional residency period. When you file the I-829, you should be free to obtain a repayment of funds. The increasing processing times resulted in "redeployment" mechanisms becoming a relevant consideration for investors.

Need to look at your project documents to see what your options are.

The funds have to be at risk until the I-829 is filed - you are years away. Plus the return of the funds is governed by your subscription agreement because these are two separate matters. You are a long way away.