The Value of Scripting

If KotBR or Squash Syndicate mean anything to you and you're in my party, then stop reading.

So, I'm a really new to DMing (I've run a couple of one-shots, but I'm finally running my first ongoing campaign; LMoP, and they just finished with the Redbrands and are about to head to Cragmaw Castle), and I've found that I've been having a lot of difficulty improvising dialogue for the various NPCs a lot of the time. Part of it is that I have a slight stutter, but a lot of it is simply having difficulty getting into the NPC's head and not coming up with meaningful dialogue quickly. Interestingly, this is not a problem I have ever had while RPing as a PC, and it has only affected my RP as a DM.

Well, since the party just hit level 3 a few of them got to do some RP between sessions (Paladin taking their oath, Warlock receiving their pact boon, Ranger meeting an Archfey and becoming a Fey Wanderer) and in preparation for these RP events I literally wrote out a script with things that the NPC would say, and sometimes things that they might say depending on the situation. I also scripted some stuff like that for Sunday's session, when I also introduced the first of two new PCs/Players to the party. I'm finding that by scripting out dialogue and events I'm able to play the NPCs in a more dynamic fashion, and even when the players inevitably go off-script I'm more comfortable playing the NPCs because the NPCs have their things that are important to them (on-script), and so they are always trying to get back to those talking points.

Anyway, I feel like this has been a bit rambly, so let me get to my question(s):

1. More experienced DMs, do you use scripting in your campaigns?
2. Is my needing to lean on scripting to improve the RP moments a failing, or a totally viable way of adapting to overcome a shortcoming?
3. What tips do you have about what to script, and what to avoid scripting?
4. What are the biggest pay-offs and the greatest dangers of using a script?
5. What non-scripting techniques do you use to improve your RP of NPCs overall? How well does this pair with scripting?