Trump's speech marked the end of a republican national convention which broke with tradition and protocols, including his decision to hold

some events at the white house, which some have criticized as an ethics violation blurring the line between campaigning and governing.

The convention targeted Trump's base as well as groups showing low support for him.

1) 上句，为什么his decision to hold.., 可以his decision holding...吗？

2）而 an ethics violation blurring the line,可否an ethics violation to blur the line ?

3)  groups showing low support, 这表明groups正持有low suppoer, 如果是groups to show low support是否意味着将来持有low support ?

4) 如果名词+不定式后置（如果是主谓结构），是否表明是“将来”的动作，而如果是名词+现在分词（肯定是主谓结构），则动作正在发生？

麻烦老师能详解，非常感谢！