Do I need to pay estimated tax for stock gains quarterly?

I am not a stock trader (at least I won't file my tax return as one who makes a living by trading stocks), so I will deal with short/long term capital gains for my trades this year.

Looking at my records, I actually have some gains for each of the third quarters so far:

Jan. 1 - March 31:   $2500 short term gain.  It's already too late to pay more estimated tax for this, but the tax amount is probably not significantly large.

June 1 - Aug. 31: $10000 short term gain.  I still have a few days before 9/15 to pay estimated tax for this.

Sept. 1 - Dec. 31 (up to Sept. 11 so far):  $64000 long term gain.  I have until 1/15/2026 for this.

I think my tax bracket is %24, so the federal tax I owe should be (2500+10000) * 0.24=3000 for first 8 months.

Looking at last year's federal tax return, I had a $7000 refund, and I may get similar refund without any capital gain this year.  That said, I don't have to pay any estimated tax for the capital gain in first 8 months of the year?  I am already paying estimated tax quarterly, and I guess I will meet the safe harbor this year.  However, I don't mind paying more estimated tax this quarter to be safe.

1. Any suggestion on federal tax? 

2. I live in California.  Do I need to do anything with franchise tax board?  No, I haven't never paid any estimated tax to the state.

3. People mentioned about form 2210 on the web.  Is that something I should check out now or only when I file my tax return next year? 

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