Never underestimate the power of misleading someone. If blacks are being recruited as bombers, then the line might go something like “Don’t worry, the bomb will be set up with more than enough time for you to walk away after pushing the button”. Instant detonations could be attributed to faulty timers, or to the bomber “not understanding his instructions”. Some black islamofascists may be willing to go the whole mile, too, particularly ex-felons who have a grudge against a particular target. Remember, this probably covers non-American blacks such as Somalis and Sudanese, too, who have different cultural mores.
They would run out of volunteers before they got any good at it.
(2) While it is possible that some American-born Islamofascists might be willing to die, it would be extremely uncharacteristic. Even hard case John Allen Muhammad surrendered rather than go out in a blaze of glory, and the scumbag Hasan Akbar - despite his psycho ramblings and the suicidal attitude revealed in his personal journals - surrendered as well.
In America, suicide just isn't considered cool or noble, and if anything African-Americans culturally disdain it more strenuously than white Americans.