Tax Credits for US Citizen Residing in Japan

[Garbanzor29]

I'm a US citizen, but I'm a permanent resident of Japan.  As such, I must report my worldwide income to BOTH countries for taxation.  I have tried and tried to find clear, simple written explanations of which country I should pay income tax to first for certain forms of income, and which country will grant me a tax credit.  And if I ask around, I get conflicting answers.   Why does this have to be so confusing?

Q:  Which country has to allow for a tax credit?
Could someone please give me a clear, simple answer for each the following:

1. US Social Security Retirement Benefits
2. Japanese Pension (Nenkin) Retirement Benefits
3. US-source Bank Interest
4. Japanese-source Bank Interest
5. US-source Dividends from Stock or Mutual Funds
6. US-source Capital Gains Distributions from Mutual Funds
7. US-source After-tax Retirement Annuity (ATRA) Income

8. US-source Government (Federal or State) Pension Income

9. US-source IRA and 401k Income 

I'd really appreciate answers, and I'm sure they'd be helpful to others, as well.

Thank you.

[TomD8]

https://www.irs.gov/pub/irs-trty/japan.pdf

[Garbanzor29]

This is not an answer.  It's merely a link to a 23-page government treaty written in legalese.  I have looked at this many times before and never been able to understand it, in large part because of the so-called "saving clause" in Article 1, paragraph 4, which makes most of the treaty irrelevant to expats like me.  

The reason I asked my question is because there is not a clear, concise answer available in this treaty, in any IRS documents I have looked at, or elsewhere online.