Ideas For Long Term Future Of Humanity

Can we move Mars (which is too cold today) closer to Sun to make is more hospitable for human life?
Could we slowdown orbital speed of Mars (to get it closer to Sun), by slowly changing orbits of selected asteroids(and comets?) to make them collide with Mars in a controlled way? (And if we continue doing that for hundreds of years.)
Colliding asteroids with Mars would also increase its mass, which is a good side effect because Mars is significantly smaller than Earth.
Colliding comets is even better because they would increase (surface) water content of Mars.
Since we know that Sun will get gradually hotter and bigger as it aged, here is an utterly insane long term plan to ensure distant future of humanity, assuming we will have the power to modify orbits of asteroids and comets such that we can make any of them collide with any planet in a controlled way so that we can increase or decrease size of the orbit of the planet (we would be also keep increasing the mass of the planet we bombard; also we could use available comets to provide extra water to target planet):

Imagine first we could bombard Mars until its climate and water content is good enough for humanity.
Then move humanity to Mars (or as much as we can),
then we could bombard Earth to increase the size of its orbit as much as we want/need.
And afterwards as the Sun keeps getting bigger/hotter,
we could keep moving humanity back and forth between Earth and Mars, and each time after we moved humanity to one of the planets, we could bombard the other planet to increase the size of its orbit as much as we want/need.

Potential problems would be, can we keep the orbits of all other planets still stable for long term,
and what are the limits of keep increasing the mass (and water) content of a planet we want to live in?
Also after how many times we moved humanity, we would run out of asteroids to use (and only can use comets)?
Could we still continue by using comets?
If so when we would run out of comets?
And if we also run out of comets, what would be the final mass (and water content) of Earth/Mars?
What would be the size of the orbit of Earth/Mars, and would there be any chance of moving humanity to any planet in any nearby star?
(Because I think if the size of the orbit is big enough, it could make it possible to come close to a suitable planet in a nearby star. Keep in mind we would prefer to save all humanity if possible.)

Another potential problem is, even if we added lots of water to Mars, how we would get a suitable atmosphere?
Assuming we have no electrical power production problem, maybe we could separate lots of water to oxygen and hydrogen gas, and release hydrogen gas to space.

But then can we live in a almost pure oxygen atmosphere?
Are the common rocks on Mars have enough nitrogen we could release to atmosphere?
Or is there any other suitable inert gas we could produce enough from the rocks?

But also how we could modify the orbits of almost any asteroid or comet?
I don’t think any kind of rocket fuel would be enough.
But assuming we can produce portable fusion power generators that can generate maybe something like megawatts for decades, it maybe possible to produce enough thrust in space using only electrical power in different ways.
One way I was thinking could be to create giant rotating electrical and/or magnetic fields around a spacecraft to swim thru sea of cosmic rays around (positive and negative charged particles) like a submarine.

Of course if we had technology to easily modify asteroid and comet orbits, it would also be useful for protecting humanity from any unwanted asteroid or comet impacts anywhere.

Also can any space habitat would be viable way to live for humanity indefinitely?
Wouldn’t it keep getting damaged by cosmic rays?
Could we always repair and protect it?

How about another crazy idea:
Could we build lots of giant towers on Earth where their tops are above the atmosphere of Earth?
If so and we also have tech to create efficient and powerful pure electric drives for space, maybe we could turn Earth itself to a mobile planet.

This maybe the craziest idea:
What if we turn Earth to a mobile planet and also bombard Mars with asteroids and comets and get it closer to Earth and also make Mars have similar amounts of water and oxygen atmosphere, and later also turn Mars to a mobile planet?
Then we would have two mobile planets to live and move anywhere, maybe even to nearby stars.
Then maybe we could keep creating more mobile planets everywhere we go in the universe.

(I had posted these above comments here about two weeks ago:
http://scienceblogs.com/startswithabang/2017/07/01/ask-ethan-could-we-save-the-earth-by-migrating-it-away-from-the-sun-synopsis)