HP 7500A Wide Format Problem

[ocd]

Hello,
I have an HP 7500A wide format printer. Two problems The first minor one is that I have to take out and replace the black ink cartridge every 3 weeks or so (20-40 pages) cause it prints like running out of ink. Just take out cartridge, put it back-works fine. This was initially worked through w/ HP help line.
The other, more significant problem is that the printer, which I special ordered this 13" x 19" paper for the wide format, only prints to maximum dimensions of about 8.5" x 12-13". My laptop is a Dell Inspiron w Windows 7, bout 18 months old. HP help line was not able to help me. We went into all special sub-menus, selecting paper size "Super B", etc. Disappointing.

Would appreciate any help. Thanks.