To answer your first question, yes, there is something you can use to remove the color from your hair, but because your hair has been bleached, I wouldn't recommend it. I think your best bet is using a permanent hair color close to your natural hair color and snipping your brittle ends.
Answer to second question: highlighting is generally more damaging than darker colors because a higher volume of peroxide is being used in the process. Example: to go from dark brown to blonde a 30 volume peroxide is used, but to go from blonde to a darker shade, a 10 volume peroxide can be used.
If you want healthy hair, I suggest you go to a professional to have your haircolor done. The boxed color at the drugstore always lies and has high volume peroxide in it, which will damage your hair even more. It sounds like you need a good cut too. Maybe a graduated cut will work for you, that way you'll have more length in the front and will still be able to clip your hair out of your face. Also, your flat iron can be your friend and your foe. Even the costly ceramic flat irons can damage your hair because you'r using high heat. Try to limit your flat iron use and ask your hairdresser for a cut that can be worn wavy. When you must go straight, be sure to use a product that protects against heat damage. I use one made by a brand called Proclaim found at Sally's Beauty Supply. It has a red cap on it. I just bought a 6 oz bottle on sale for $4.99! Lastly, I would suggest that you purchase a shampoo that is pH balanced (your hairdresser should know). I hope I've helped you out some.