I’m saying your interpretation of the treaty is incorrect. Immediately after the two sentences you quoted is a third one clarifying that the “rights and obligations arising from the [NPT] will continue to apply to the united Germany”, meaning that Germany retains the right to withdraw from the NPT under Article X like any other signatory.
The Treaty on the Final Settlement with Respect to Germany restored the country’s full sovereignty. The positions it reaffirms don’t limit what Germany is allowed to do under other treaties. It doesn’t prevent Germany withdrawing from the NPT. It doesn’t prevent Germany from doing anything that other sovereign states can do.
Germany bought a small number (35) US fighter jets as replacement for the aging Panavia Tornado used as bombers carrying US nuclear weapons as they are not allowed by their allies to have their own.
This is a very weird claim. If Germany wanted to build its own nuclear bombs, it could withdraw from the Treaty on the Non-Proliferation of Nuclear Weapons. Germany could also have asked to host French nuclear missiles instead of US nuclear bombs, possibly as part of an EU-wide agreement rather than a bilateral deal.
The letter and spirit of the paragraph both seem quite clear to me. The united Germany was to become party to the same treaties as West and East Germany with regard to nuclear, biological and chemical weapons. The NPT is the legal text of the “renunciation” of nuclear weapons, even though that specific word doesn’t actually appear in the NPT. Germany’s rights and obligations under the NPT are the same as those of all other signatories.