You have great evidence of bonafide marriage. Joint bank account is worth opening for reasons beyond immigration. In my family, it helped combining funds for paying off mortgage, car loans, utilities and other recurring expenses. It won't look fishy. Also, you can open free joint checking / HYSA accounts to keep emergency fund or save towards vacation or other goals.
I hope you filed taxes jointly? In overwhelming majority of cases, joint filings make better financial sense for the family as you get bigger tax break. If this is the case, include joint IRS tax return transcripts in your I-751 packet. These are downloadable for free from IRS website.