Does my spouse have to be in the US with me when we file our I-485?
Yes. In order to file an I-485, you must be in the US.
If you are in the US and your spouse is abroad, then you can file the I-485 for yourself and your spouse will have to undergo consular processing.
For your spouse to be eligible for consular processing, they will have to wait for your I-485 to be approved and then file the I-824 to have the USCIS send the approval notice to the National Visa Center. Once the National Visa Center receives your approval notice, then consular processing can begin. This process takes significantly longer than if your spouse stays in the US and files the I-485 with you.