They actually do look pretty good!
If you're unsure about the whippiness, I'd try more hair and more backcombing. The more hair you push to the top, the more you can pull back down to create the dread taper. As for bumps, that can be irradicated in the backcombing stage. Literally every couple of combs, pull the hair back down, feel how solid it is, and if it's not even all the way down then pull the bump apart before backcombing it any further.
In the past if I've come to seal a dread and there's an unslightly bump, I've cut the worst out and wrapped around it. If it's just dreads for yourself then that's an okay technique (I wouldn't do that for something I sold!).
With the ends, there's plenty of ways to do it - there are discussions on here. Flat irons are a good method, or what I do with mine is twist very tightly and blast a hairdryer at the ends. It's solid but not melted and can be snipped very neatly
