My messages are overloading my storage on my 2nd gen iPad, but I cannot get to the function at all to delete them

For some time now, I have not been able to access Messages from Settings on my iPad 2. When I try, it either freezes up, or I finally get to a sign in screen, but my login info isn't accepted. I do not use the messages function on the iPad; its gets the messages from 2 phone numbers (both 4S), but if I delete either of the numbers from the Messages function on the iPad, it messes up the messaging on our phones, between the two (both are on the same apple ID). My storage on the iPad is almost full. The messages comprise ove 1G. I need help, please! Thank you!