Immigration officials are already overworked, grumpy and, from my experience, generally seem to regret their life decisions. The ability to fill out the forms in perfect formal kanji hiragana/katakana will be an asset to help smooth things over. Also, your spouse will be able to more fully answer seemingly mundane and baffling questions than someone not familiar with the Japanese mindset could do (N/A, non-specific answers and blank spaces don’t fly).
When communicating with immigration officials have your spouse do all the talking in Japanese and just keep quiet. They will speak English to you, but their attitude will markedly change if forced to do so.
If you already have a spousal visa, and had to go to the Tokyo Regional Immigration Bureau, I am guessing you know how traumatically Kafkaesque the ordeal can be (For the uninitiated: Be ready for bizarre 1930s style bureaucracy and a symphony of languages and smells. Try to use the bathroom before you get there and touch as little as possible- my wife caught norovirus after our last visit. This may be difficult because the bureau is in the middle of nowhere so you’ll be spending most of your day there traveling to and from and waiting 4-6 hours for your number to be called). Like @Isodora said, if it all possible, hire an immigration lawyer to do the legwork for you.
When submitting supporting financial documentation take the shotgun approach. Submit every bank account, 401k, pension account, brokerage account, income source and asset you have. The goal is to try to make yourself look as rich as possible. If you’re volunteering don’t forget to include that as well (seen as an asset to society).
I don’t think you mentioned how long you’ve been living with your spouse but this will make a difference -the longer the better.
Using the methods I mentioned I had no snags with my application and, although I don’t remember the exact time frame, I do remember getting my card on almost the exact day that immigration had estimated.
You may hit a brick wall if you have missed even one tax/Insurance payment to the Japanese government, let your residence card expire, been convicted of a crime anywhere in the world or come from an “undesirable” country.
Baring any of the above since your spouse can be your guarantor you have a greater chance than most of success. Japan needs you to “go forth and multiply” and create little taxpayers so our social insurance (public pension etc.) doesn’t become insolvent
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