I am a bit late coming to this discussion and there is not a whole lot more I can add to what has been said (but I’ll try anyway!). You should only continue riding if you enjoy it, not through some bloody mindedness. But it sounds like you have set yourself a steeper challenge than most of us did. You have a heavy bike and you have gravel roads, that’s a tough combination for anyone to start learning on. It sounds like you are being too hard on yourself over a couple of low speed drops (and I mean drop, not crash). It is much harder to ride at 5mph than 50mph. Those of us who managed to avoid dropping our bikes in the early stages certainly came close. It mostly boils down to luck, not skill. By practicing you build your skill levels but you run the risk of dropping it. Double edged sword but you need to build your skills somehow. It took me close to 4 months of PLP before I could do the box easily and even now, if I do not practice, I get rusty.
You seem like a thoughtful person who has taken the time to learn what needs to be done. Now it just takes time for it all to come together. I wish you all the best in your endeavors but I honestly feel you are just down after some bad moments. Hang in there and I think it will all come together. Good luck!