Welcome to the forum LAMAR__44 ...here are my thoughts to give some correction and guidance:
pleasure is the sole good, and pain is the sole evil, everything else that we should pursue has the characteristic of being instrumental towards pleasure, and everything we avoid has the characteristic of being instrumental towards pain. This helps significantly in judging what is worthy of pursuit and what isn’t.
I think that your wording here makes for an incorrect understanding and application -- the meaning of the word "sole" = only. This sets you up for a big problem, because sometimes we do what is needed for good health and for long-term happiness. If you think with the word "sole" the error could be that your pleasure has to be sensory oriented or somehow a big pleasure. And it is important to understand that anything that we do that doesn't contain painful sensations is also labeled "a pleasure". We also see in the letter to Menoeceus: "And since pleasure is the first good and natural to us, for this very reason we do not choose every pleasure, but sometimes we pass over many pleasures, when greater discomfort accrues to us as the result of them: and similarly we think many pains better than pleasures, since a greater pleasure comes to us when we have endured pains for a long time. Every pleasure then because of its natural kinship to us is good, yet not every pleasure is to be chosen: even as every pain also is an evil, yet not all are always of a nature to be avoided."
it’s hard for me to think of this with relationships. I think it makes sense to evaluate before starting a friendship or romantic relationship whether there will be net pleasure or pain, but doing this inside of relationships seems to make them feel shallow and transactional, at least for me.
Your error here is in thinking too abstractly (net pleasure vs net pain). I think most people wouldn't tolerate a friend who seems to criticize all the time or who is impatient or unkind - we all know how to instinctively avoid these people. Even if the person is a family member (sibling, etc) then we make sure to keep our distance (for self-protection). So as soon as we sense that a potential friend has those characteristics, we should have no qualms in steering clear of making friends with a person like this.
I must say that there is no intrinsic value in my relationships with my loved ones, they only have value in so that they’re instrumental to my pleasure, but in doing this, I lower my experience of pleasure within these relationships. But that would result in less net pleasure then if I decided to disbelieve in hedonism, so to live according to hedonism, I need to disbelieve in hedonism.
First, regarding your cognition of "pleasure" in relationships -- if you think too abstractly then perhaps that is why you may be for some reason not feeling enjoyment. Joy is a feeling, and it has concrete and specific causes. All relationships are about about a type of "inter-dependence"...meaning that we "inter-are" and we experience things based on what all the people in the relationship do. Pleasure not only comes from what my loved ones do, but pleasure also comes when I give pleasure to my loved ones.
You don't choose your family, but you choose your friends -- so potentially your friends will be bringing more love and acceptance into your connection and interactions (for example, since in friendships there won't be any conscious or unconscious sibling rivalry that could occur in family relationships).
Regarding your idea of "no intrinsic value except through being instrumental for pleasure" -- there is an error of thinking here also -- because you are again stuck in a concept and have forgotten your heart. The sense of our heart contains the emotions and feelings together with breath of the body and the feelings of aliveness. All of this is the reason why it says in the Principal Doctrines: PD27. "Of all the things which wisdom acquires to produce the blessedness of the complete life, far the greatest is the possession of friendship."