I wish I had a picture of my tank before it was sandblasted. Between spending 16 years in New York state and being on a Holiday Rambler with an aluminum body shell (electrolysis) it looked pretty awful. Areas of my tank that cleaned up beautifully looked very similar to the first post pictures. The rust forms flakey scale which looks worse than it is. If the OP decides to sandblast it, it's a simple matter to take it off and cover the valves and information placard with silver vent tape prior to sandblasting and repainting. My tank is a 32 gallon tank and it cost me $50 to have it sandblasted and primered and $20 for paint. Not a bad price to pay for a tank that could easily be mistaken as being brand new.
Steve