The ranks will be very different to canon. I also changed the race of the demon Judah (Chapter 2) since I realised he was too weak to be a marquis. Also some of the stats that's been shown from Chapter 5 and below have been changed. I wrote >(edited)< next to the things I changed in order to help you understand. And yeah, sorry about that.
{Rimuru's World Ranks}
SS Rank: 5,000,000+ EP (Catastrophe Class)
S Rank: 2,000,000+ EP (Disaster Class)
Special A Rank: 1,000,000+ EP (Calamity Class)
A+ Rank: 200,000+ EP (High Level Hazard Class)
A Rank: 100,000+ EP (Low Level Hazard Class)
A- Rank: 9,000+EP
B+ Rank: 7,000+ EP
B Rank: 5,000+ EP
B- Rank: 4,000+ EP
C+ Rank: 3, 000+ EP
C Rank: 2,500+ EP
C- Rank: 2,000+ EP
D Rank: 1,500+ EP
E Rank: 1,000+ EP
F Rank: 500+ EP
{Spirit World Ranks} (This is not canon as I purely made this for fan fic)
Primordial: 1,000,000+ EP
Arch Duke: 750,000+ EP
Duke: 500,000+ EP
Marquis : 320,000+ EP
Count: 300,000+ EP
Viscount: 275,000+ EP
Baron: 250,000+ EP
Baronet: 220,000+ EP
Chavalier: 200,000+ EP
Greater Demon: 100,000+ EP
Lesser Demon: 50,000+ EP
{Unknown Beings In The Tensura Verse} (This is not canon as I purely made this for fan fic)
God Class: ???
Demi-God Class: 10,000,000+ EP
True Dragon Class: 5,000,000+ EP
High Level Deity Class: 1,000,000+ EP
Low Level Deity Class: 500,000+ EP