Planning An Epic Symphonic Poem

Hello guys! So i've recently taken on the task of writing a symphonic poem based on a story. The entire work (if performed) will probably be divided up into two sections by an intermission. I'd like some advice on how to develop this piece because I want it to have "movements" but it isint supposed to be a symphony. It's sort of like a ballet, without the dancing. Something akin to Firebird.

I've been composing for about three years and i've always done incidental music. I'd really like to use this chance to work on developing ideas and leitmotifs and intertwining them to make a big work. So i've divided the story into multiple sections, each with movements. Each of the movements will seamlessly transition into eachother, except for the intermission point (which has yet to be determined.) The piece is based off a story from the Elder Scrolls series, about the creation of the world. This is my plan:

1: Nothing, and Everything
- Before, Forever (Opening theme)
- Anu, The Glacier (Anu's Motif)
- Padomay, The Storm (Padomay's Motif)

2: Time is a Dragon
- Akatosh, the Dragon (Akatosh's Motif)
- Lorkhan, the Fox (Lorkhan's Motif)
- What's Bigger than This? (Lorkhan sees beyond reality)

3: Multiplication
- Our Ancestors (The Aedra's Motif)
- Not Our Ancestors (The Daedra's Motif)
- And Everyone Inbetween (The Et'Ada and the Magna-Ge)

4: Blueprints in Braille
- Seducing a Dragon (Lorkhan convinces Akatosh to build the world with him)
- Magnus, the Engineer (Magnus's Motif)
- Hardhats Only Beyond This Point (The World is constructed)

5: A Wheel or Tower
- Former Friends (The Daedra mock Lorkhan)
- A Grand Finale (The World is finished)
- End Scene (The Gods gather for the grand opening)

6: Mousetrap
- Liar (Lorkhan's plan is discovered, Magnus flees)
- Prison Bars (The Gods are trapped in the World)
- Rat Race (Akatosh is trapped in the current of time)

7: The End of the Beginning
- Trinimac, the Hammer (Trinimac's Motif)
- Heartless (Trinimac tears out Lorkhan's Heart)
- Spinning (Finale)

Each movement looks like this "- Spinning (Finale)" and the titles with the numbers are sections. There will be many themes depicting characters, and those themes will appear in later movements, leitmotifs. Should I go ahead and plan what themes appear in what movement on paper. And should I develope all those themes and leitmotifs before I start composing? I've already done detailed planning until section 4 "Blueprints and Braile"... but I want to make sure I'm doing this correctly or if y'all have any advice for me.

Thank you!