First let me say:

1. It was Nicodemus (and you presumably knew that), when he throws something small to/at you, a coin is a reasonable assumption. You had options to deflect or dodge, perhaps much like Harry, your subconscious made a decision for you...

Now to the other hand:

2. Harry considers a glove and a crown royal bag sufficient. There's no indication that the cloth need be blessed.

3. A shadow could have done very little to you. Indeed without first knowingly using some of its power, it couldn't even appear to you as itself; it would have to deceive you.

So there are cases where your GM is not staying true to canon.

Your bit about how your character can only be described as a LG Paladin however, might indicate this isn't the best fit for you either. Canonically, there are about 3 people who would never [insert specific violation of moral code here], and they all carry the swords. Most of the books are about the fact that the characters keep having to things which are clearly gray areas. Theoretically, your story could be about how you never ever ever ever fall to temptation, on the other hand that likely means the situations you are in aren't tempting enough.

If you're not in a situation where the power of a fallen angel might make the difference between success and dying, how terrible could the bad guys really be.