Kindle newbie here, I have several questions!

Helloo! I picked up a Kindle Fire 7 a couple of days ago in the black Friday sales and I'm nothing but impressed with it, brilliant little thing when I only paid £35 for it but I have a few questions -

The lock screen adverts. Is there a way to pay amazon to remove them? Also there was nothing on the box or in the instructions about ads which is slightly misleading. I know selling ad space keeps the cost of the tablet but honestly, showing it to a friend and the unlock screen was for womens razors.. yeah.. Is there any reason why charging is painfully slow? My ancient S3 charges faster. I gather it runs on a heavily modified version of Android (Heck, when I plugged it into my laptop it had the android folder), is is possible to run droid apps? Seems wasteful to have to re-buy all the apps I have on google play :/

From a newb, thanks for taking the time to read.