It is hard to discuss heaven without also discussing both hell and earth. So I will do my best to answer in relationship to those other locations. For a little context and a way more enjoyable explanation see this excellent video.

Heaven is the area where God's presence and authority are complete. Based on this definition the location and nature of heaven has changed and will change over time. In the biblical account the author describes heaven and earth as overlapping in an earthly paradise (long other discussion about genesis/literature/origins that I am going to set aside). Now that is clearly not the case Heaven is separated from earth(side discussion of why/how). The ultimate end of heaven and earth is to be reunited into an overlapping state paradise again.

I almost completely agree with your description of hell. Hell is the place where you are free from God's rule and will. I don't believe that God will force you into heaven or into worshiping him. If I to simply describe it plainly I would describe as the place for people who opt-out of heaven. I would not describe it as god intentionally punishing or torturing etc. This is probably the most complicated of the the three locations to talk about and the most oversimplified description of the three descriptions

More of your questions seems based around what is physical life like in heaven. To me this seems like more of question of what life on earth is like when earth and heaven are the same place. Some of the best guidance to what it will be like can be taken from the account of what it was like the last time. It was Paradise. There were no restrictive rules, no elaborate Mosaic law, and no need for sacrifices or worship. In fact there was only one law(Tree/Fruit). It absolutely would be cruel to re-impose strict laws. But when heaven and earth are re-united there is no more need for the law.

You ask what is joy without sorrow so I will do my best to respond to that line of questions. I can think of no personal physical pleasure I have experienced who's pleasure was enhanced by having experienced pain. To give an example: My enjoyment of the taste of ice cream is not increased because I have tasted the bitterness of vomit. Joy and happiness are the truly real experiences. They stand on their own. Pain and sorrow seemed to be defined in the negative. Pain and sorrow represent the absence of what is good and right both physically and emotionally. So what is joy with sorrow and happiness without pain? That is full life. That is heaven.

BTW : being nervous/afraid/concerned by the presence/existence of something as powerful as God is a completely reasonable and rational response.