the dslchecker definitely shows you max expected to be 52mb which is the same as attainable on the hub stats. your low speed problem is due to the unstable connection which resulted in DLM putting your line in a banded profile at a reduced speed of 35mb to try and stabilise your connection once you have stable connection for a few weeks then banding will release and speed increase
your neighbour could be on a different nearer cab than you and before you ask - no you can't be change to that cabinet