I'm sorry not to be able to help you right away with DCG, I used to use it but it was a few years ago, atm I fly scripted linear campaigns.
Something strikes me though, you mention multiplayer ?
DCG can be played in single player too AFAIK, you generate your new mission after playing previous and find it somewhere in your single missions folder.
Your conf.ini is identical to mine except for this line
EnableResize=1
If you have black bars anywhere on your screen it may prove helpful, otherwise just ignore it.
The other part of your conf.ini you want to check (for best quality) is
[Render_OpenGL]
TexQual=3
TexMipFilter=3
TexCompress=0
TexFlags.UseDither=0
TexFlags.UseAlpha=0
TexFlags.UseIndex=0
TexFlags.PolygonStipple=1
TexFlags.UseClampedSprites=0
TexFlags.DrawLandByTriangles=1
TexFlags.UseVertexArrays=1
TexFlags.DisableAPIExtensions=0
TexFlags.ARBMultitextureExt=1
TexFlags.TexEnvCombineExt=1
TexFlags.SecondaryColorExt=1
TexFlags.VertexArrayExt=1
TexFlags.ClipHintExt=0
TexFlags.UsePaletteExt=0
TexFlags.TexAnisotropicExt=1
TexFlags.TexCompressARBExt=1
TexFlags.TexEnvCombine4NV=1
TexFlags.TexEnvCombineDot3=1
TexFlags.DepthClampNV=1
TexFlags.SeparateSpecular=1
TexFlags.TextureShaderNV=1
HardwareShaders=1
Shadows=2
Specular=2
SpecularLight=2
DiffuseLight=2
DynamicalLights=1
MeshDetail=2
VisibilityDistance=3
Sky=2
Forest=3
LandShading=3
LandDetails=2
LandGeom=3
TexLarge=1
TexLandQual=3
TexLandLarge=1
VideoSetupId=2
Water=4
Effects=1
ForceShaders1x=0
PolygonOffsetFactor=-0.15
PolygonOffsetUnits=-3.0
Be sure to select openGL as render in settings, quit game, THEN check your conf.ini vs mine.
Have fun