Untrue, read russian forum stuff.
Some screens have nonstandard sizes. Do you make so many layouts?
Really, you can move this components. But i mean de-facto it irrationally, because you should create LayoutParams objects and setParams. With code method you doing this is to create an interface.
This difference is so small that it can be neglected
1) You didn't read my whole paragraph on that. I know that 1dp != 1px in general.
2) You should make a version of your drawables for each hdpi, mdpi, and ldpi and include them in the appropriate folders. Layout XML files should be placed in either layout-land, or layout-port and then,when referencing a drawable, the android system will determine which one to use.
3) Due to poor English (I'm not insulting you, some people don't speak English natively, and I ma aware of this), I do not understand the third comment
4) Yes, this is true, but you were saying XML files had high overhead. While XML files do have overhead, float calculations are much less efficient, even though both are negligable.
I see that there is no swaying you from your decision to use programmatic UI development, but it should be noted that, unlike Java SE, Google intends Android UI to be done via XML, and standards exist to be adhered to. Although you might see your code has being better, when it goes against standards, it doesn't matter if it truly is better, it will be snared at by other developers.