Health: I have no financial interest in pushing Yashan nor am I foolish enough to rely on statistics from organizations that do.
Winter wheat and Durham wheat have very different characteristics, and you cannot combine them to create a rov. Winter wheat is low gluten and creates a crunchy product, while Durham wheat is the opposite. You are correct that any product containing solely winter wheat, such as pretzels would not be an issue with its flour content. However, pretzels usually contain malt which is a chodosh concern. Most products contain a blend and at least partially consist of Durham wheat, which is primarily chodosh. If that portion is at least 1/60 of the product, it may be assur min haTorah.
You are correct that rye is not a problem.
You are completely incorrect regarding oats. According to the USDA, North Dakota grows the most oats of all states. They plant between May 2-17 and harvest Aug 11-27, just over 3 months. Early May is usually after Pesach, and it will all be chodosh.
Barley is a big problem, and avoiding it in cholent will not solve your problem. Beer is derived from barley, as is malt. Many products today contain malt, including corn flakes, rice crispies, rice cakes, pretzels etc.
Avoiding pasta is also inconsequential, as most pastries contain more than 2% Durham wheat.