In the claustrophobia of a haunted flat, an immature voodoo sorcerer makes a terrible choice when he calls upon his dark gods to seek revenge for a broken heart.

You are hiding the ball by describing your second act as a "terrible choice". This vague description encompasses the main plot and your entire second act, one half of the story (one hour for a movie).

"Gee Bob, let's go see a movie tonight. How about a cool movie where the sorcerer makes a terrible choice."

Please give us more than a vague reference to your main conflict.

Loglines are a great tool to keep you focused on the big picture. What you described is a vague idea.

If you know what you are writing, state it.

I'm also a supporter of changing male main characters to female unless there's a compelling reason not to, and this looks like a good opportunity to engage more of a female audience.

That's very long, and doesn't provide a clear picture of the story. Also: not sure voodoo is the same as sorcery. But this has to be cleared up and cut down. I'm a big believer in stating four basics, and that's all: protagonist, goal, antagonist, obstacle. All other details can be provided in longer summaries. So it might work more like this:

A heartbroken young man summons voodoo spirits to exact revenge on his ex-girlfriend, but must save himself when they turn against him.

Or:

A heartbroken young man must save his soul when the voodoo spirits he summoned to punish his ex-girlfriend turn against him instead.

Or you could do it this way, though I think it's often stronger to identify the main character immediately: After summoning voodoo spirits to punish his ex-girlfriend, a heartbroken young man must save his soul when they come after him instead.

One thing you'll really want to think about is how to get across the genre. Is it true horror/thriller, or more of a dark comedy? It could go either way, but you want to have the concept made clear by the words you choose.