It is not important what Islam itself says in relation to the things Hamas does because its more important what Hamas thinks.
They have a very specific view of martyrdom that absolutely serves their own aims, ends and purposes.
Put it this way, Hamas has an ideology that is Jihadist in nature and, whilst it is not mainstream Islamist, it is a subset of it.
There is a difference between Jihadism and Islamism. This is from the BBC in 2014 - consider it as a primer:
https://www.bbc.com/news/world-middle-east-30411519
So, does Jihadism reward Hamas terrorists and other like-minded terrorist organisations?
Yes - the best known example is the concept of 72 virgins in Heaven.
IMO, you have to draw a clear distinction between the religious belief system of Islam and the terrorist belief system of Jihad.
Doing so also means an individual would be much less likely to fall into the problem of Islamophobia since you're showing you understand the important differences between them.
More, importantly, you can distinguish between them.