Haha, Golem... I think you're reading a bit too much into it...
That's what makes it fun- reading into it

He may be an arrogant, self-obsessed lunatic... and he may be a little overzealous in his desire to abandon the Wasted Earth and find a new home among the stars... but I don't think that that has anything at all to do with his desire for control and power and "Order" (which is largely what you have described). His unwillingness to share has less to do with his Megalomania... and more to do with the fact that there is nobody worthy of his trust to SHARE with... save perhaps maybe for The Courier (assuming you don't betray him).
And what does THAT tell you? The fact that over two hundred years he hasn't found a single person in the whole wide world to share his vision with?
The Earth is not salvageable. It will -never- be like it used to.
Millions of years of life has been wiped out... entire continents have been lost... those species that -do- remain, have been forever tainted by massive amounts of radiation and exposure to god-only-knows how many different mutated diseases. The New Plague is still looming out there, somewhere... Limit 115... and there is obviously enough F.E.V. still lurking in dark holes in the ground to give anyone with half a brain cause for concern. The ecosystem is unstable. The weather patterns are in chaos. The few 'nations' powerful enough to rise up from the sand are too busy squabbling over old-world tech to realize they need to rebuild... and when you try to talk sense to them... they decide to try and have you killed.
Why rebuild? Why even bother? How can anyone hope to be successful?
Fair enough. Now balance that with colonizing a whole new planet you don't know a damn thing about.
For one, it's going to have a different star. Completely different solar radiation output- not just intensity but also different spectrum. The ecosystem will be stable but completely alien; you could encounter creatures that would make Deathclaws look tame, or pathogens that put FEV to shame. Or high concentrations of something nasty, like arsenic, in soil and water. Or any number of absolutely unforeseeable other surprises. Seismic activity could be ten times Earth's, etc. At least on Earth you're dealing with the devil you more or less know by now. Plus a small group's chances of survival are by definition lower than a large group's.
Perhaps House has a method of keeping his colonists alive we haven't heard of... perhaps he intends to use the technology which preserved the likes of the Vault 112 residents... or like himself...
He isn't in a terribly good shape these days, is he? He preserved his mind, but hardly the body. And if it's the best he could do for his own self...
With large enough vessels and sufficient enough technology, food and water could be produced right on board...
Produced out of what? What is the ship going to produce them out of? Suppose hydroponics solve the air recycling problem, water could be recirculated (although never without loss)- but where is the ship going to get the nutrients required to grow food on board once the original supply runs out?
Could he do that in fifty years? Maybe... maybe not...
... but he most certainly isn't going to need THOUSANDS...
For launching the project? He wouldn't. For completing it? Actually finding a habitable planet and relocating humanity there? You betcha.
and I don't think he ever mentioned to the courier whether or not he planned to simply blast them off into space without a destination.
You reckon he already knows a habitable planet?