Hi @MichaelJuan.198
1. You can use an online tool such as Date Calculator to figure out exact date. Based on what you said, the earliest you can file I-751 is September 27th, 2023. But no harm if you file few days later. It's even better to ensure you're in 90 day window.
2. Photos are somewhat weak evidence. You should submit them, but more importantly, include:
lease or mortgage with both names on it, joint bank account statements, utility bills in both names, flight and hotel reservations in both names, medical insurance with both names, IRS joint tax return transcripts, birth certificates of children and many more.
Spend good time to prepare evidence. Strong evidence reduces chance of RFE or denial.
3. You can apply while I-751 is still pending. You don't have to wait to file for N-400 but it will only be approved when I-751 is approved. Yea, they still do combo interview, but not always. That's always been the case.