Thanks for uploading a better quality image, it's much easier to see everything now. Your idea for the Tri-River sounds good. It was the only element of the map that looked odd to me, everything else was clear enough to read. Are you going to be adding more elements besides the marsh or caves/cliffs near Tri-River? I think it would really make your map look much better. In my opinion black and white seems to fit nicely with your style.
I know that some people here in the Guild, when drawing by hand on a paper larger than A4, scan their drawings in stages and then "stitch" the parts in a graphic program. You might try doing that. Though I suppose drawing on a smaller format will be easier...