Yowza Slash Chords!! - this looks fun.
So i guess, what is the easiest way for you to think about them? There's a bunch of different ways of writing the same chord.
I don't know if I'd count them as suspended chords. To me a sus chords doesn't have a 3rd.
For example: D11sus4 (add3) is just an inversion of a D11
Since you've got the whole things as slash chords (i assume to specify the inversions) you'd probably leave it, but in other contexts you can simplify.
So if you take that mentality, You could probably write some things a little simpler too (at least i find this simpler). so one chord as opposed to two on top of each other.
For example
Intro:
A#/Csus4 - (C-F-G-Bb-D-F)
Gmin7/C
1st bar/2nd bar.
D-G-A-C-E-F#-B - D13sus4 (add3) - Cmaj7b5/Dsus4
D13
D-G-A-C-E-F#-A - D11sus4 (add3) - C6b5/Dsus4
D11
3rd bar/4th bar.
D#-G#-A#-C-D#-F## – D#6/11sus4 (add 3) - Cm/D#sus4
Eb6add11
D#-G#-A#-B-D#-F - D#sus4 (add #5)(add 9) - B(b5)/D#sus4
Abmin6/Eb
5th bar/6th bar.
C#-F#-G#-A#-C#-F – C#sus4(add 6) (add 3) – Bb/C#sus4
C#6 (add11) or F#Maj9/C#
C#-F#-G#-A-C#-E – C#sus4(add b6) (add b3) – A/C#sus4
C#min6 (add11)
7th bar.
D-G-A-C-E-F#-A - D11sus4 (add3) - C6b5/Dsus4
D11
8th bar.
C-F-G-Bb-D - C9sus4 – Bb/Csus4
C9sus4
If it's easier for you to think as slash chords, then the only thing i'd change is in the Intro and last bar I don't think you need to denote A#/E# in the treble as it's just an inversion and the bass note is somewhere else entirely but the chord hasn't changed.
As I said, it's what ever works for you in your mind. Theory is just a way for you to understand the structure and turn it into music.