I would enjoy being in a permanent state of bliss/non-suffering. All volitional actions are done to alleviate suffering of some sort - do you have examples of any such action that does not fit that case?
Well according to the definition you gave of activity, it says that activity is that which is required to improve one's own situation (or to alleviate one's own suffering basically). That's why I asked why all activity has to be selfish.
There are plenty of activities or actions that are not aimed at improving one's own situation, or alleviating one's own suffering. All kinds of actions are aimed at alleviating the suffering of others instead of yourself. And there are also actions that aren't related to suffering at all (even using the extremely broad definition of it in Buddhism). Things such as praising God, for example. If someone is praising God, they aren't currently in a state of suffering. They are currently in a state of thankfulness for something God has done for them, or in a state of amazement at something God has done in general, or in a state of awe about God Himself. None of these things entail suffering.
I think everyone would long to be in a permanent state of bliss, and the idea of alleviating suffering in the world seems a noble concept. But it seems to me that the Buddha's definition of both suffering and activity are quite skewed. He seems to only focus on one's own suffering, for one thing, and not the sufferings of others. By saying that even breathing is suffering, and basically everything in life is suffering, causes a complete discontentedness about everything in life. There are plenty of people in the world who are very thankful to be breathing right now after the things they've gone through. The breath of life is a blessing, not a suffering.
Suffering means enduring with patience. It doesn't necessarily have to do with enduring hardships, but it can include that as well. And the reason for suffering isn't that our expectations are too high. The reason for suffering is that we are in a fallen world corrupted by sin.
His teachings don't allow for any type of interaction with one another, or with God, since all actions indicate that some type of personal suffering is occurring, and the end goal is to end suffering, and therefore to cease all activity. So then there is no love in his teachings. There is no meaning to life in his teachings (except that life equals suffering). And even if the highest end were to be in a perpetual state of meditative bliss, what authority does he have to make the claim that anyone could achieve that goal? Obviously that goal can't be attained in this life, so then it would have to occur after this life. And what authority or knowledge did he have about our state of being after death, never having died as yet?
There is no way to escape the existential. Once you exist, you exist. Your soul is housed in your body, and once the body fails, the soul leaves the body. And what happens to the soul afterward is determined by what the soul did when it was housed in the body. If the soul sinned, it will suffer death. If the soul did not sin, it will live. But everyone ever born has sinned, and is therefore under condemnation. God Himself had to become a man so that He could live a life in a human body without sin, so that His righteousness and sinlessness could be placed on us by our faith in Him (God manifest in the flesh, who is Jesus Christ, the Messiah). He lived His life in a body here on earth without sin, fulfilling the entire law of God, and then died on the cross willingly and purposely, shedding His blood in our place, having our sins nailed to the cross with Him, so that our sins (and ultimately, our sufferings) could be eradicated. This is the only way out of suffering. Jesus said that if we believe not that He is the Messiah, that we will die in our sins (which means that our souls will suffer the second death, physical death being the first.)
There are only two choices: life or death. There is no other state of being, and the Buddha, being a man born under Adam and in a fallen state himself, had no authority to claim otherwise.
Jesus Christ is the only way out of suffering.