In article , jacob navia
writes:

Note that
paradigm changes are painful but I hope people proposing a new one
won't have the problems of Galileo...

A man does not attain the status of Galileo merely because he is persecuted;
he must also be right.

---Stephen Jay Gould

1) We have a really MASSIVE cluster at 10 GY from here (3.7 from
the supposed "bang").

Right.

Note that the lensing confirms the big mass
of that cluster.

Right.

How can such a monster cluster evolve in just
3.7 GY? A galaxy merger takes like 1GY, and the central galaxy
must have done some to acquire its size.

You are making a common error: rejecting an entire paradigm because of
problems with details. Yes, if such details persist, then it might
indicate a real problem. However, structure formation is very difficult
to model compared with cosmological tests which lead to the currently
accepted "standard model".

The center of the arc
is the central cluster galaxy.

The arc is the background galaxy at higher redshift. It isn't in the
lensing cluster. Its position with respect to the lensing cluster is
also not at the center. The arc is at the edge of the cluster (as seen
on the sky). You misunderstood the abstract.

2) The lensing implies that there is a BIG galaxy much farther away,

No. It implies only that there is a galaxy farther away. (It appears
bug because of the magnification due to the lensing effect). The
question is how likely it is to have a galaxy at this redshift, not its
size.

so much farther away that it is lensed by the cluster. Then, several
questions are raised: How come that there are so many big galaxies
behind that cluster that we see a lensing effect?
Galaxies should be smaller approaching the supposed "bang"! But no,
there are so many big ones that we see a lensed one.

Again, I think you misunderstand. The lensing effect magnifies the size
of the galaxy (and, since it conserves surface brightness, also makes it
brighter.)