Half Marathon Training Plan

I need help from my fellow runners! I tweaked a 21 week schedule that gets me through training for my first half marathon (S&S is Strength and Stretching). Can you give me some feedback? Any tips or any week that looks out of whack?

Week	Monday	Tuesday	Wednesday	Thursday	Friday	Saturday	Sunday	Total Miles
December 12th	S & S	3 miles	2 miles	3 mi + Strength	Rest	30 min walking	4 miles	12
December 19th	S & S	3 miles	2 miles	3.5 mi + Strength	Rest	30 min walking	4 miles	12.5
December 26th	S & S	3.5 miles	2 miles	3.5 mi + Strength	Rest	40 min walking	5 miles	14
January 2nd	S & S	3.5 miles	2 miles	3.5 mi + Strength	Rest	40 min walking	5 miles	14
January 9th	S & S	4 miles	2 miles	4 mi + Strength	Rest	40 min walking	6 miles	16
January 16th	S & S	4 miles	2 miles	4 mi + Strength	Rest	50 min walking	6 miles	16
January 23rd	S & S	4 miles	2 miles	4 mi + Strength	Rest	50 min walking	7 miles	17
January 30th	S & S	4.5 miles	3 miles	4.5 mi + Strength	Rest	50 min walking	7 miles	19
February 6th	S & S	4.5 miles	3 miles	4.5 mi + Strength	Rest	50 min walking	8 miles	20
February 13th	S & S	4.5 miles	3 miles	4.5 mi + Strength	Rest	50 min walking	9 miles	21
February 20th	S & S	5 miles	3 miles	5 mi + Strength	Rest	60 min walking	9 miles	22
February 27th	S & S	5 miles	3 miles	5 mi + Strength	Rest	60 min walking	10 miles	23
March 5th	S & S	5 miles	3 miles	5 mi + Strength	Rest	Rest	10K Race	19
March 12th	S & S	5 miles	3 miles	5 mi + Strength	Rest	60 min walking	11 miles	24
March 19th	S & S	5.5 miles	3 miles	5 mi + Strength	Rest	60 min walking	11 miles	24.5
March 26th	S & S	5.5 miles	3 miles	5.5 mi + Strength	Rest	60 min walking	12 miles	26
April 2nd	S & S	5.5 miles	3 miles	5.5 mi + Strength	Rest	60 min walking	12 miles	26
April 9th	S & S	5.5 miles	3 miles	5.5 mi + Strength	Rest	60 min walking	13 miles	27
April 16th	S & S	5.5 miles	3 miles	5.5 mi + Strength	Rest	60 min walking	13 miles	27
April 23rd	S & S	5 miles	2 miles	5 mi + Strength	Rest	Rest	8 miles	20
April 30th	S & S	4 miles	2 miles	2 miles	Rest	Rest	Half Marathon	21