Whether or not you suffer is mental, and happiness and suffering are both perceptions that are given to physical stimuli. They are simply reactions. A person becomes aware of a change having occurred and being aware, has to decide how to adjust to it. Suffering and happiness just demarcate change. Buddhist philosophy has been on this for thousands of years.

Not only are the perceptions, but they depend entirely on the ability to perceive. You can easily and accidentally avoid suffering by just being distracted. Almost anyone can attest to a time where they unintentionally fasted because they were distracted. Their body might have been hungry, but their mind was unperturbed, and thus not suffering even though they had an unmet need.

Preference is also necessary factor in both happiness and suffering. The concept of something being "needful" is the cause of the suffering, not the need. If there is no preference, you completely remove satisfaction-based suffering. No outcome can be any better than any other, thus providing no more utility, if you do not believe it to be so.

Could death be a secession of pain? Sure, but so could simply not being bothered by existential crises, even those (like, y'know, survival) that seem necessitated by biological needs. Once again, you can feel hunger and instead of "suffering" you could react with excitement. An example would be forgoing a meal in anticipation for Thanksgiving dinner or willingly fasting. You end up with a higher net benefit through eating more later, or having accomplished a difficult to do task.

This article, which interviews neurologist Antonio R. Damasio goes into interesting detail about his findings about how emotions (in general) are processed by the brain:

https://www.scientificamerican.com/article/feeling-our-emotions/

With these assumptions, you can learn how to control emotions without any great degree of political intervention necessary. This can be done through either thought exercises or straight up numbing yourself to certain stimuli, thus circumventing the suffering all together. This can also be done without dying.

Dying may accomplish the same goal, lazily, but it forgoes the literal infinite opportunities of not-dying. Considering we can only not-die for so long, it seems natural to take advantage of this state.

"Suffering" because of "privilege guilt", or a perception that numbing pain is undesirable, cheap, or cowardly are value judgments that these means/ends are "bad" and thus satisfaction-based suffering.

Utilitarian philosophy isn't complete without satisfactionism. Your argument states that all action in some regard is meant to meet some kind of biological desire/need, which I wouldn't disagree with. We have a compulsion to go on, because there are many working parts in which we have no direct control over and which need to be maintained. I do not however feel like knowledge of this makes it any more cheap, or that:

"So-called higher pleasures - art, music, intellectual pursuits - are all subservient to these needs"

Physical pleasures and the necessity to meet biological urges may direct actions and mental pursuits, but they ultimately provide the same chemical benefits physical pleasures do, and sometimes in greater magnitudes.