The asker seems to be looking more for a method than for an answer. My method was a bit different to everyone else's, so even though it comes out to the same answer I felt it would be appropriate to write it up. Hopefully someone finds it useful.
Method
For this answer, "Rule" will mean a set of up to 16 characters in specific locations, combined with two numbers representing the Correct and Rightly-placed characters in that set. We begin this puzzle with three Rules.
Rule 1: K B C 8 2 W % T + 7 E R 4 9 6 A 10/8
Rule 2: A K T 1 % 3 R @ W D M F 8 5 9 7 9/8
Rule 3: K B F 8 2 W 4 T + 7 5 R C 9 1 A 10/3
The method I used to solve this puzzle was to compare and combine the Rules we have in order to create new Rules. I am aiming to create perfect Rules: rules that contain only correct and rightly placed characters. The closer a rule is to being perfect, the more useful it is. For example:
Recognising that Rules 1 and 3 are similar, we can separate the commonalities from the differences to create 3 new rules from those two.
Rule 4: K B 8 2 W T + 7 R 9 A
from both
Rule 5: C % E 4 6
from R1
Rule 6: F 4 5 C 1
from R3
Since no more than 3 characters in Rule 4 can be rightly-placed (from Rule 3), all 5 characters in Rule 5 must be rightly-placed (from Rule 1),
Rule 4: K B 8 2 W T + 7 R 9 A 5/3
Rule 5: C % E 4 6 5/5
and no characters in Rule 6 can be rightly-placed, though they must all be correct
Rule 6: F 4 5 C 1 5/0
Note that Rule 5 is a perfect rule: it has 5 characters in the set, and all 5 of them are correct and rightly-placed. To solve this puzzle, just continue experimenting with breaking down the rules you have into rules that are closer to perfect until you get to the answer.
Answer, continued
From here, we can also note that from Rules 5 and 6 we know 8 of the 16 correct characters. Separating the characters we know must be in the final result from Rule 2, we can create two new Rules:
Rule 7: A K T 3 R @ W D M 8 9 7 5/5
Rule 8: 1 F 5 3/3
Rule 8.5: % 1/0
5 characters in Rule 7 must be Correct, since we have removed 4 correct characters from Rule 2. No more than 3 characters in Rule 8 can be Rightly-placed, so 5 or more characters in Rule 7 must be Rightly-placed to match '8R' from Rule 2. Therefore, logically, Rule 7 must have 5 Correct and Rightly-placed characters, and Rule 8 becomes perfect with 3 Correct and Rightly Placed characters.
Now, using both Rule 5 and Rule 8, we have 8 characters correct and rightly-placed. We can get the rest by comparing and combining Rules 4 and 7 to create 3 new rules:
Note that Rules 4 and 7 share no characters with the 8 that we know from Rules 5 and 8. They contain only the 8 unknown characters, and must contain all of them. Between them they have 10 correct characters, so two of them must be shared between the two rules. Rule 4 has 3 rightly-placed characters, and Rule 7 has 5, so the shared characters will be rightly-placed in Rule 7.
Separate the shared characters into one rule with placement from Rule 7, and the not-shared characters into two other rules:
Rule 9 : A K T W 8 9 7 2/2
from shared chars
Rule 10: B 2 + R 3/3
from R4
Rule 11: 3 R @ D M 3/3
from R7
We now have 5 rules which contain all 16 characters correct and rightly-placed. Compare them and resolve the overlaps:
Rule 5 : C % E 4 6 5/5
Rule 8 : 1 F 5 3/3
Rule 9 : A K T W 8 9 7 2/2
Rule 10: B 2 + R 3/3
Rule 11: 3 R @ D M 3/3
Rules 5, 8, 10 and 11 resolve simply. Rules 5 and 8 are perfect (containing no incorrect characters) and Rules 10 and 11 become perfect after removing the characters that overlap R5/8: (R, R and M)
Rule 12: B C 1 2 3 % @ + D E F 4 5 6 14/14
Rule 9 : A K T W 8 9 7 2/2
Rule 9 can be perfected by removing overlaps with Rule 12, and the puzzle is solved in Rule 13:
Rule 13: A B C 1 2 3 % @ + D E F 4 5 6 7 16/16