How can my spouse be added to my EB-5 case if we got married after my I-526 approval?

The I-485 of your husband has been filed. The time to ask these questions is before his I-485 is filed. If his I-485 filing includes proof that he and you were married after your I-526 petition was approved, then this should be sufficient.

There is no problem to add a following to join spouse, however, presently the China (assuming both you and he are subject to the Chinese quota) Final Action Date is backlogged to 08JUL15. If your case was only filed in August 2015, he will have to wait until this priority date or Final Action Date is current and a visa available.

He can file an adjustment if he is in status and you married before the I-485 was approved.

If you were married before you received a conditional green card, your spouse should be able to file I-485 as your derivative beneficiary based on your approved I-526. It appears you have indicated your spouse already filed I-485 as your derivative beneficiary.

I-526 is irrelevant here. Sponsor your spouse as the marriage took place after you filed I-485.

So long as you were married before you received your conditional green card, your spouse can obtain a green card based on your approved I-526 as your derivative applicant. It sounds like your husband already filed Form I-485 and therefore will be receiving a green card along with you.