1) Through deductions, most of the people making within the raised zero tax level were already paying nothing. This makes things easier but not really much cheaper.
Do you not know how taxes work? They are tiered. Meaning that for EVERYONE the first 24k is tax free. That is the same for billionaires. Their first 24k is tax free. Then the next say 24k-100k pay at 15%. That means that 66k is taxed at 15%. Your first 24k is still tax free. Then 100k-250k that is taxed at say 20%. Meaning 150k is taxed at 20%, 66k taxed at 15% and 24k not taxed. Then any money over 250k is taxed at say 30%.
I've heard people before say, if I make any more money I will jump up a tax bracket and then make less money overall. That is not true. That is not how taxes work. A friend used to tell me this when I was young about how his dad got a raise and made less money due to that. It's not true.
2) While the standard deduction is increased, many itemized deductions have been eliminated which again leaves most people close to breaking even, or possibly paying more if they were in a situation which benefited from deductions (ie States with high income taxes, families with numerous children, people with high student loan interest, people with high medical bills, etc).
Have you ever worked at a tax firm? Done taxes for a tax season for people before? I have. I've done thousands of taxes. Little heads up. 90% of middle class or lower people are not itemizing their deductions. The standard deduction is usually the higher of the two. And that was when it was at 6k. Double that and it don't matter if none of the itemized deductions are being dropped or not, the new 12k will be higher than most all standard deductions.
Most of the Itemized clients where those that were in the 200k or more. You know people who were able to donate say 10k to their church or other big itemizations.
3) Similar to above, while the child tax credit is increased from 1k to 1.6k, they are cutting the dependent exemption of $4k. That means for middle and upper income families with multiple children, the extra $600 of credits may not cover the loss of $4000 of exemptions.
And for an analysis of where the savings go if you want to look past how things sound in theory and into how they work in practice, look to the Tax Policy Center's analysis of the Unified Framework plan:
As you can see, middle and low income individuals get around a 0.2% to 1% boost in after tax income on average (as previously stated, depending on specific situations certain individuals will be paying more) while those in the top 5% of income get about an 8-10% boost in after tax income. Virtually all of the direct benefit of this plan falls onto corporations and the very wealthy.
Now, you might be thinking "well a cup of coffee is better than nothing", but you also have to consider the effects of decreased government revenue on different populations. Primarily the negative impacts of increased federal debt which is felt by everybody and in the long term could easily overtake any miniscule benefit these tax breaks have on the poor and middle class. Then there is how government outlays have to adapt to lowered revenue. As we have seen with the Republican budget, this typically involves cutting programs which disproportionately help the poor such as Medicare/Medicaid and the SNAP program, which will often leave lower income individuals having to pay more out of pocket, reducing their real spending power.
My two cents on a couple of your points.
No comment on #3 since been a couple years since did taxes so don't recall on where the exemptions kick in. If before AGI, after, and so on. So I'd rather not make a comment on something I'm not concrete on.