What difficulties do non-state actors (i.e terrorist groups) face when they attempt to effectively acquire and disseminate biological weapons?
Terrorist groups often have limited resources: So would a few difficulties include: lack of sufficient technical and scientific knowledge to effectively produce, weaponize, and disseminate a lethal strain of a virus, along with other operational, and organizational deficiencies?
The issues that you mention are definitely important issues that are faced by non-state actors. It is very difficult to create biological weapons in the first place. Trying to do so in a situation where you have to try to avoid detection would be more difficult still.
A second problem that such actors face is the fact that states would be very reluctant to help terrorist groups acquire the ability to use biological weapons. States would fear at least two things. First, they would fear that the terrorist groups might one day turn the weapons on them. Second, they would fear that the world might find out they had helped the terrorists to acquire the weapons. If this were discovered, their country would be likely to face retaliation, particularly if the terrorists had actually used the weapons.
For these reasons, it is very difficult for non-state actors to acquire and use biological weapons.