How to calculate class 4 on second job?

If I had one PAYE job, which paid about £22000 on which I have paid £855 class one NI contributions, then I became self employed with £12000 net income, it looks like I pay £12000 * 9% = 1080 in NI contributions. Is that correct? Does the "Lower Profits Limit - Self-employed people start paying Class 4 National Insurance" not apply because I earned more than £12,570 income from my PAYE job? Also, does the £1000 trading allowance still apply? (as in, could I be reporting 11000 not 12000?)

Hi

If you are employed, but also do self-employed work, your employer will deduct your Class 1 National Insurance from your wages.  
You may also have to pay Class 4 National Insurance for your self-employed work.  How much you pay depends on your combined wages and your self-employed work.  
HMRC will let you know how much National Insurance is due after you’ve filed your Self Assessment tax return.

Thank you

This is not a helpful answer. I need to make decisions and manage my finances with knowledge, not luck; I should be able to understand how this works. There are two general questions here that should be quite answerable: 1. Does the "Lower Profits Limit - Self-employed people start paying Class 4 National Insurance" not apply if you earn more than £12,570 income from a PAYE job? 2. Does the £1000 trading allowance still apply if you also have a PAYE job.

Hi,
The Lower Profit Limit for class 4 applies only to the profits from self employment, the PAYE income is not taken into account for calculating class 4.
You should also be aware of the Small Profit Threshold for Class 2 NI which is payable of S/E profits over £6725 (24/25 rate).
Thank you.