Self-employed sole proprietor with W2 income

Let's consider a hypothetical tax environment I may end up in 2021 and try to find legit answers.

 

Household: Single, no dependents

Business type: Software services

 

Source of income:

  1. C2C contract as a sole proprietorships
  2. W2 employment, employer withheld taxes

Expected total gross income:

  1. $180 000 from sole proprietorships business
  2. $130 000 from W2 employment

Retirement total contributions:

a) $45 000 (25%) to SEP simple from sole proprietorships income

b) nothing from W2

 

Questions:

1. Does pass-though 20% deductible applicable for remaining taxable $135000 from business regardless W2 taxable $130000?

 

2. What's the difference between 157000 and 207000 thresholds for single when we are talking about qualification for pass-though 20% deductible?

 

3. Now let's add additional information.  There is an accumulated $100 000 investment loss carried over from 2019. What is an additional deductible we can consider from both sources of income after 20% pass-through? 

 

4. What should I keep an eye on to minimize tax withholdings for the given example?