Those Enneagram guesses for Frodo and Sam sound about right.
Merry did seem to me to be a thinking type - he handles everything actually pretty calmly and I don't think ever has a very big emotional reaction. ESTJ could be possible, I suppose. Hobbits in general seem to be very S, and he came across as N in comparison with them.
For Aragorn:
INFJ, though I could also see ISFP or ISTP. 8w9 Sx/Sp
I said P because he really doesn't want to be responsible for being the one leading or making decisions, at least at first. Though he does deal with it and become more J later on, so yeah. Hmm... Not sure he seems very 8 to me.
Gandalf always seemed pretty F to me. Why did you think INTJ?
Gimli:
I saw him as ESFP, but now that you mention it, his commentary is very Ne-ish at times. 8w7 So/Sx
Gimli as 8... Yes, that definitely fits
Yeah, I didn't really have a clue with Legolas. I nearly put him as S because he does seem to be S comnpared to other elves...just not in comparison to everyone else.
For Boromir:
Yeah, could be. I didn't have much of an idea for him either.
For Faramir:
I think he's ISTP (didn't see much Ne) maybe 3w4 for his enneagram? (2w3 is possible)
He does seem quite focused on the "big picture" (i.e. long term damage of keeping the ring, while Boromir was more focused on the short term value of it), which is why I said N. I said E because his whole "charismatic and universally adored" thing is more commonly found in E's and there didn't seem much to indicate either way otherwise. Though I'll admit I don't particularly buy him as ENTP, ESTP or INTP may be more realistic. For enneagram, he seems to be more motivated by approval and inter-personal stuff like a 2 than achievement for it's own sake like a 3.