Upgrading a entry level hybrid bike or purchasing a new better one
Upgrading an existing bike piecemeal is always going to be more expensive than buying a new bike with the specs you want, because manufacturers get components at a discount.
Regarding Option 1, upgraded components will not transmit more stress to the frame, if that's what you're asking. It is possible (but seems unlikely) that the frame was engineered with just enough safety margin to allow for light trail riding, but not more intense off-road riding. I wouldn't let that guide my decision.
The gravel-bike category is a broad one, and some bikes are more road-ish, others are more MTB-ish.
If you frequently cover both tarmac and dirt in a single ride, that sounds like a good argument for a gravel bike. Everything is a compromise, and you need to figure out what compromise you're most comfortable with.