If I own 0 battlefields and I'm 1 point from winning but I use Hostile Takeover on an enemy unit, do I score a hold point and win the game?

No, you do not win the game by scoring a "Hold" point. You would potentially win the game through a Conquer point, but not a Hold point.

According to RiftJudge FAQ #9236, using Hostile Takeover to take control of an opponent's only unit at a battlefield does not count as "holding" that battlefield. Instead, it initiates a noncombat showdown, which results in you establishing control and performing a Conquer.

Here is the breakdown of why you cannot win via a "Hold" point in this scenario:

1. Hold vs. Conquer: "Hold" points are only awarded during your Beginning Phase (Rule 464.2). Using a spell like Hostile Takeover during your Main Phase to seize a battlefield results in a "Conquer" (Rule 464.1), not a "Hold."
2. Scoring the Win: While you would gain a point for the Conquer (if you haven't already scored that battlefield this turn), this does not satisfy the requirement for a "Hold" victory.
3. The Victory Condition: If this Conquer grants you the final point needed to reach the Victory Score, you will win the game. However, it is explicitly classified as a Conquer victory, not a Hold victory.

Summary of your sequence:

• Hostile Takeover resolves: You take control of the unit.
• Noncombat Showdown begins: You become the controller of the battlefield.
• Conquer: Because you just gained control and haven't scored that battlefield yet this turn, you gain 1 point (Rule 464.1).
• Victory: If this point brings you to the required Victory Score, you win the game at that moment (Rule 467).

You do not score a "Hold" point, as hold points are strictly awarded at the start of your turn for units already present there.