How to prep and level part of my garage when there is a 6" difference in hight?

Specs:

• Garage floor is cement
• 24’x32′ (except where the car will park.)
• far side is approximately 6"lower than the other. (~1° slope)
• large crack running the full length.
• a number of smaller cracks.
• some old oil stains.

What I’ve got so far:

1. Power wash the floor of the garage.
2. Scrub and remove oil stains. (What do I use?)
3. Let fully dry. (How long?)
4. Use angle grinder with concrete cutting wheel to clean up and widened crack.
   Update: Recommended to use a concrete saw instead.
5. Fill crack. (Bondo All Purpose Putty?)
6. Update: Use a Bonding Agent between the layers. (Something like Latex Drylok Bonding Agent?)
7. Use something between 2×4 studs/base plate to separate the cement and the wood and keep the cement from filling the stud bay. (Flashing maybe?)
8. Caulk cracks at base plate. (Silicone?)
9. Build Walls and seal gaps. (Silicone?)
10. Mix and pour cement. (What cement should I use keeping cost and simplicity in mind?)
11. Tool the cement so it’s level.

Notes:

• planning to use epoxy coating for floor.
• prefer to use something that is simple but cost effective. (If you can call any of this simple)
• will not pour where car is going to park.
• will be both a workshop and a garage.

Questions:

• Am I missing any steps?
• What are good products to use given the depth of the pour goes from 0" to 6"?