[Erik]

It should seal to your body everywhere, especially at the torso. 54 sounds right: my Picasso was a 52Long as I'm 6'1" and about 10 lbs lighter.
The only way to know is get in the water and do some good dives over 10 metres...if you have cold water constantly flushing through, you'll need alterations or exchange for a slimmer suit. If it's tight, no problem unless you are restricted at the neck and blood flow is interrupted to your bean! It'll stretch out in any case and a tighter suit to begin with is a better way to start.
Peace,
Erik Y.