Bow Evolution

Technically, the bow was a military weapon in Korea until 1894.  Also, Koreans believe they and Manchus are directly connected to each other, that Manchus are a break-off from Koreans.

Here is from correspondence Peter Dekker and I had a few months ago on the subject (I just put my part of the conversation):

It is mainly translations from Korean, so some romanization, interpretation, etc. might be different from what's in books written in English.  Also, things are not necessarily in order, as the info came from various Korean sources.

1. Ching's motto was 愛新刻羅: "Love of Silla (a Korean kingdom) is carved in our hearts". 
2. Ching's ancestry is from the Jurchen, who established the Jin (Keum/Kim) dynasty. 
3. The Manchus were a branch of the Joseon people from Baekdu Mountain.
4. The first ancestor of Jin (Kim) was Kim Haeng (Kim Ham-bo), who was the great-grandson of the last king of Silla, King Gyeong-sun.  The king's son, the grandfather of Kim Ham-bo, Maeuitaeja, went into a deep mountain and never returned.
5. Kim Ham-bo's people failed to gain back Silla from Goryeo, so they went north.
8. Nurhaci, who was born around Baekdu Mountain, founded the Later Jin (Kim) dynasty, which later became Ching.
9. Nurhaci called his dynasty Later Jin (Kim) because his ancestor built Jin (Kim)
10. During the 1592-98 Japanese invasion of Korea, Nurhaci sent a letter to Joseon stating that, "Rats invaded my parents' country!"

Remember that the Japanese yumi came after the Korean bow, and Korean archery had already matured by that time.  Also, if you look at the Japanese release, it is very similar to the Chinese style, along with a seldom-seen, old Korean style of release.

At least in some parts of Korean history, yes--for instance, in battle with the Japanese in the 1592-98 Imjin War.  Shipboard archers shot fire arrows at Japanese ships.  Here is from an exhibit at the War Memorial in Seoul dramatizing it (you can't really see it, but the archers are on a ship):

When the Japanese first invaded, the Korean land forces were near non-existent, while the Korean navy was strong and experienced, having been fighting pirates for years.  The Japanese situation was the opposite; their land forces were strong, but their naval forces were little more than a giant ferry service for the land forces.  The reason why the Korean navy was not able to quickly stem the flow of Japanese land forces was because Admiral Yi Sun-shin didn't even learn of the invasion until three days after it began; even then, it was another fifteen days before the king gave him a mandate to take military action against them!

Regarding the bows in particular, first, nowadays, Korean archers use their horn bows in all kinds of weather; in wet weather, they are just careful to wipe them off if they get wet.  Second, as mentioned before, it is unlikely most enlisted archers had horn bows, due to their cost; they couldn't afford them and the gov't certainly wasn't going to pay for them.  Chances are, they were more likely some type of self bows or bamboo bows, which the archers could either make themselves or have made inexpensively.

It's hard to say, as there is not much left from that time period.  What Koreans called a wood bow ("mokgung"--목궁/木弓) was actually a composite bow of bamboo and wood; there is an original left and I have one of only two reproductions of it in the world.

Original

Reproduction

Amazing bow, what is the length of the mokgung when strung? 

Also what kind of draw weight would the "regular" soldier or sailor been using?

The wooden bows almost look like the illlegitimate love child of a Scythian and Turkish bow.