Whole 20 filled to the top with Anubias.

I started a tank with manure and potting soil a couple years
back and threw in some fern, anubias, and crypts. I set the
light on a timer and pretty much got busy with other things and
neglected it, only feeding the fish a few times a week. Now I
see, the anubias took over and the crypt and fern are small and
stunted. The whole tank is filled to the top with anubias and
I can't budge the thing. Something seems stuck good.

I want to move them to a larger tank, my concerns a
If I pull up the anubias, are the roots deeply imbedded in the
potting soil, manure and gravel mix, will it release the rotten
sulfur gasses and kill the fish too? Will I mess up the
plant's establishment and large growth if I move them? What if
I cut them, how should I cut it? I can't trace because I can't
see where the roots start and begin, there are green branches
all over and white roots sticking out everywhere.

I want to move the anubias, if I knew this was going to happen,
I would've started with a larger tank when I first began. If
possible, I'd like to keep the whole plant as big as possible
and not have to fragment it.

Thanks all.