Re: Otto Link pitch issues
No, that's really not it. Mouthpieces vary in length. When I first played tenor (after playing clarinet and alto). I was way sharp for a long time with 7* tips. I finally (finally is the key word, because it took about a year) took more mouthpiece in my mouth, dropped embouchure pressure way down, and now I play in tune with all of my mouthpieces near the center of the cork. Note, the shank length on my mouthpieces are all different.
Someone else stated it earlier. You went from a 2.5 reed on a 4 mouthpiece to a 7* mouthpiece. To play the 7* you need to close that reed further to sound a note, because of the larger tip opening, and you are doing that by pinching which takes you sharp. You should try a 2.0 reed, and take a look at where the reed first touches the rails as you follow the reed from the tip to the table. Where the reed touches the rails is where your embouchure should be. The tendency, when moving to larger tip mouthpieces, is to leave your embouchure where it was on the 4, which would be too close to the tip. Since the 7* has a longer length of reed not touching the rails, your embouchure needs to be out there to avoid having your embouchure effectively shorten the vibrating length of the reed.
The first time you try a 2.0 reed and moving your embouchure back to the new reed to rail separation point, it will feel and sound a little strange. But like anything else, give it a little time and you may find that it helps a lot. Note this approach helps a lot with getting good, clear low B and Bb tones as well.
Good Luck, and be patient. It takes most of us many, many years to learn how to play the way you would like to play.