Marvin, I'm so sorry for your wife's deterioration, and this decision that you have to make.
First, do you know, or can you guess, what her own wishes would be? Had you ever discussed this, even in passing? Her choice, if you know it, should be the deciding factor, of course.
There are two separate emotional issues going on ... one, the FTD, and the other, the emotional lability of
ALS, which can be treated. I suspect that the aggressiveness is connected to the emotional lability, which means that with the proper medication, she would not be as aggressive or hostile.
If she has trouble swallowing, this could be contributing to her rapid decline. Has she lost much weight? If she can keep her weight up, possibly her progression would slow.
This is a very, very personal decision. As I see it, the pro's of the feeding tube are that she would regain strength, and possibly slow down the progression of the disease. Also, she would be free of the fear and frustrations in swallowing.
The con would be that if she is not rational and is agressive, management of the feeding tube would be very difficult, and possibly distressing to her.
I'm sure you will make the right decision for her, but I know how hard this must be.
God bless.