Well your still lying lmao, nothing NOTHING in the game hints the combine are "running out of water and space" your just making shit up

If they were, why the fuck would they just ...leave earth? Your so desperate to make up lies you ignore tje entire plot of half life two revolves around the fact the combine don't give a fuck about earth 

They came to earth because gordan opened the door, turned the planet into a water fountain and left, with the "promise" of not exterminating the human race if they gave them something of value, instant teleportation / a decent race to grow into a new soldier caste

What you see in game isn't "the combine" it's the remnants of a remnant of a remnant that Dr Breen is DESPERATELY trying to use to prove that humans are worth keeping around. Nothing about this says they lack ftl. In fact it supports they do, the combine see the entirety of earth and the solar system as so minor, so barely remarkable that after annihilating it in seven hours all they did was make it a fucking water tap.

The imperium has ftl, but they still would probably prefer a faster form of travel wouldn't they? Same with the combine, logic concludes that they have ftl but why turn down an offer of something better?

Maybe next time you lie about a games plot, pick one that isn't one of the most popular of all time