Question 3 Quickies: でも, な-adjective, and "explanatory の" (redux)

Hello, friends:

I was re-reading a short paragraph in Minna last night about ninjas. I had read this material a few weeks ago, so I had intended this to be an enjoyable review. I noticed, however, that a few small points had earlier escaped my notice. Although I could be dismayed by possible Japanese regression, perhaps on the other hand I should take heart that upon re-reading I did at least see things I hadn't before. Improvement?

Ok, enough blather. Here are my questions:

1. I'm interested in the でも of the following: 目や耳かよかったから、遠い所よく見えた。小さい音でもよく聞こえた。I don't see how this could be で + も, so I looked up the meaning of でも and learned that it can mean more than "but" or "nevertheless". It could also mean "no matter how", or "even if", or "as well". These definitions would fit the context of the sentence. So in this case would でも here replace the が that we would normally expect with 聞こえる as も would on its own?
2. I have a question about the のだ in the following: 忍者はとても速く動いたり、いろいろな道具を使ったりした。それで普通の人ができないことができたのだ。 I'm thinking that the のだ here is "explanatory の". Some people may remember my travails with の (instead of ん) earlier. If this is indeed explanatory の, I totally missed it the first time I read this sentence. I'm translating these sentences as: "Ninjas moved very fast, and used various implements/devices, and so they could do things that most people could not."
3. Lastly, I'm embarrassed to ask what seems so basic a question, but here goes. When a な-adjective is separated from the noun it's modifying, does it drop the な ending? Here's the sentence that got me wondering: 家の中にはいろいろ面白い物がある。The いろいろ doesn't have its な ending, even though it precedes the noun 物 which it modifies. I swear that I read my Minna grammar explanations faithfully, but I don't recall this particular point being discussed.

That's it! I think these questions are pretty simple and straightforward and won't take much effort for anyone to answer...thanks so much!

1. Yes you are right. This でも means "even" as in "even quiet sounds could be heard" (or, if the speaker is referring to him/herself, it would be "I could hear even quiet sounds"). It is clear from the context: the first sentences mentions eyes and ears, and the second sentence is explaining just how good the hearing is. I guess you could say でも replaces が in this case.
2. If I remember your other thread correctly, yes this is another example of what was discussed in that thread with のだ/のです
3. I think this one requires Toritoribe-san's help. To me it looks like they could have included the な here. To me いろいろな面白い物 sounds correct. Leaving it off doesn't make it incorrect - it maybe just makes it more conversational. I am not a native speaker though, and am often surprised at how much I don't know.

If you have picked up these things on rereading the passages, I think its a very good sign of progress.

few typos
目や耳がよかったから、遠い所がよく見えた。

3)
Actually, いろいろ is an adverb modifying ある there.

いろいろ【色色】の意味
2 ［副］さまざま。あれこれ。種々。「色色（と）やってみたが駄目だった」「種類が色色（と）ある」
色色（いろいろ）の意味 - goo国語辞典
(副 refers to 副詞, i.e, "adverb".)

色々 いろいろ
Na-adjective, No-adjective, Adverb, Adverb taking the 'to' particle, Noun

In fact, the word order can be changed to 家の中には面白い物がいろいろある. If it's an adjective modfying 面白い物, the attributive form いろいろな is used, as Majestic-san wrote. いろいろ面白い物がある and いろいろな面白い物がある are the same in meanings, though. 少し, たくさん or some other words have a similar usage.
e.g.
少しお金を持っている。/お金を少し持っている。
少しのお金を持っている。
I have a little money.

彼には沢山友だちがいる。/彼には友だちが沢山いる。
彼には沢山の友だちがいる。
He has many friends.

However, note that there are some cases where the meaning differs whether it's an adverb or adjective.
e.g.
車をいろいろ直した。
いろいろな車を直した。

The former means "I repaired a car variously", i.e, "I repaired various parts of a car", whereas the latter is "I repaired various cars."

Hi, Majestic-sama & Toritoribe-sama:

Thanks very much for your replies and explanations. Sorry about my が typos; my proof-reading was careless but as always your keen eyes are never fooled.

It hadn't occurred to me that いろいろ could be an adverb. It makes perfect sense now. The information about word order in the sentence, and about potential meaning changes whether adjective or adverb was interesting. Very good to know!

Thank you both!

And Majestic-sama, thanks for your encouraging words about improvement. You are too kind but I will keep plugging away to try to prove you right!