Accepting an answer is not mandatory. Also, accepting an answer indicates to the community that you feel the question has been answered to your satisfaction.
Hence, to answer your subquestions:
accepting an answer just because it came first means you reduce the likelihood of getting further answers from other users. That might be okay, and is really up to you. It is always the asker's prerogative whether to accept an answer, when to do so, and which answer if any to accept.
accepting a sub-par answer that doesn't really answer your question is the wrong thing to do at best, and outright counterproductive at worst. If an answer outright doesn't answer the question, then flag it as "not an answer" to push it into the review queues for the community to look more closely at. If the answer is missing aspects that are stated in the question and you feel are important, but the parts that are in there are good and relevant, then comment on the answer to request clarification or improvement. Commenting on any post requires 50 reputation.
If a question has been sitting for a while and not received what you feel is a good answer (in my experience this happens rarely on our site, but you seem to have encountered it with a large fraction of your questions), you have two main courses of action:
Bring it up in chat. There's usually people hanging out in our main site chat room Worldbuilders' General Chat, and this can draw attention to your question. Make sure to not spam the room, and stay around to act on possible feedback. Depending on the time of day (the chat room is least active in UTC morning) it may take some time to get feedback, but chat is a good way to handle those quick back-and-forth discussions that are sometimes needed to turn a question from just-not-quite-closeworthy to great. Talk in chat requires that you have at least 20 reputation.
Offer a bounty on the question. This provides increased visibility, as well as an additional incentive for people to answer the question (they might gain some extra reputation essentially for free). Given that you currently have only 85 rep, you may not want to do this just yet (the lower limit is 75 rep for the privilege, and you can bounty off between 50 and 500 rep per question, leaving you with a maximum of 35 rep after offering the bounty; check the list of privileges to see what this would mean in practice), but it is definitely an option once you have earned a bit more reputation on the site. Do note that bounties are 100% non-refundable once started.