No, I am afraid you're wrong! The BT hardware keyboards that can be used together with iPad (or iPhone) HAS NOT the possibility of using "fn+Backspace" as a Forward Delete key, because the iOS DOES NOT SUPPORT that Forward Delete key!
Just try with Apple's own hardware keyboard with the iPad, and you will see that this basic functionality does not exist, and that fact is really incredible, and very user unfriendly. It must be Apple's stubbornness or total lack of taking into account the basic functionality of a keyboard. How can it be so?!
I know it does not exist and I did not write that you can summon a "del-key" using a physical keyboard. No I clearly said your mixing devices and you still do.
You could not use any del key, even if you were able to plug in a USB or serial keyboard (this actually is NOT possible)...
I miss this function but its not that big of a deal to start worrying about it. Calm down and enjoy the pros of your iPad.