Spouse visa after separation

i been here in japan since 2011 married to a permanent resident. my wife a single
mother so i was only one working for us providing everything. ever since my visa granted to me is always 1 yr its my 8th year now and this year i had a new company and started my shakai hokken. i paid my taxes regularly since i worked at a construction company. im waiting for the result of my new extension. on the process i had a marriage problem that will result to separation.
my question are.

1. can i change my visa if separated from spouse?
2. since there no divorce in my country should i file for annulment?
3. can i change my address easily and change whats written in my family registration or it will be changed to a new one since i will be living alone?
thank you for your answer

I suggest talking with an attorney, since many Japanese cities sponsor regular free consultations with an attorney to discuss things like this. Contact you local city hall and inquire about signing up. If there's no free consultation with a lawyer in your city, there is probably a department at city hall that can at least give you some advice. And if that doesn't help answer your question, try contacting the immigration office closest to you. Ultimately, you're going to have to deal with them anyway.

you qualify for long time residence but you need lawyer
and you be paying all your tax.
ministry of just may grant you special permit to stay in japan.

1. can i change my visa if separated from spouse?
You can change to a working visa or student visa. If you fail to find a job/school to sponsor your visa, you will have to leave Japan. Divorce means that you will no longer be in Japan under spouse visa.
my visa granted to me is always 1 yr its my 8th
This is not a good sign. It seems that the immigration office were thinking that the marriage is not stable or sham. For this reason, they were checking you up for 8 years. Normally, 3 years visa is granted in the third renewal.
my wife a single mother
This means that the child is not yours. Since you are not the father of the child, so I doubt you can get a visa to sponsor the child. You are not eligible to be Special Permanent Resident. You may have to ask the immigration office for confirmation.