You are falling into the trap of applying concepts that arise from "morphic reality theory" or dynamic timelines into fixed timelines. The paradoxes you listed are precisely the result of a dynamic timeline. There are 3 types of time travel that are typically explored in fiction.
1. Fixed timelines. Everything that happened, happened, and will continue to happen. The grandfather paradox or the bomb paradox that you talked about simply cannot happen in this type of time travel. It might be hard to come to terms with this concept if you get into the mentality that you can "beat" fate or something by doing this or that. Everything you try to do to change the past already happened before you even try it, you were just not aware of it at the time. You go back and kill Hitler and replace him with a different baby. Turns out, this new baby actually became the Hitler we know today. You or anyone else can keep trying in any conceivable way, but time is not malleable to change and everything that you tried actually already happened and will continue to happen. The paradox often presented in fixed timelines is the causal loop. In the Hitler example, we only went back in time to kill Hitler because he is evil. But by going to the past and replacing the baby, we created the evil Hitler. Which came first? Cannot be answered. Time just is. Yes, free will is an illusion in this setting.
(Ex. Primer, Predestination, Time Crimes, 12 Monkeys)
2. Multiple timelines. There are infinite universes of all possibilities. Any decision you (or anything else) make creates a branching pathway in an infinitely sprawling tree. There are essentially no paradoxes here because every alternate timeline/universe that we look into are essentially independent of each other. We go back and kill Hitler. Nothing happens in your original timeline, other than you not existing there anymore. The timeline where you kill Hitler will not have him there anymore. Doing stuff in the past will not affect you or your original timeline in any way.
(Ex. Marvel universe)
3. Dynamic timelines. Changes in the past will be reflected in the present/future. This is the most often explored type of time travel in fiction. While the fixed timelines cause the most mind fuck and "whoa" moments, dynamic timelines generally creates the bigger stakes and is great for entertainment. However, it runs into so many paradoxes and plot holes, especially if handled poorly. Your time bomb example and grandfather paradoxes fit into this type of time travel. Changing the past will often negate the purpose/cause of time travel and that is very often just handwaived away. They set certain rules regarding time travel that is inevitably broken for the convenience of the narrative. I think the problems usually arise when they try to incorporate certain concepts from fixed timelines when the timeline clearly isn't fixed.
(Ex. Back to the Future, Looper, Butterfly Effect, X-men: Days of Future past, and many many others)