Tense and meaning

Dear teachers,

What is the difference in meaning between these sentences ?

1) a) It is (high) time I / we went. (it is a little late ?)
b) It is (high) time for us to go. (the correct time has arrived ?)

2) a) It is (high) time they were married. (describes a state, a situation ?)
b) It is (high) time they married. (describes an action ?)

3) a) I was talking to Tom the other day. (= casual event ?)
(emphasis on the conversation: we were having a conversation when something happened)

b) I talked to Tom the other day. (= premeditated event ?)
(the subject did take the initiative of the action or he informed Tom about what he and other people agreed upon ?)

4) a) What were you doing in my room? (could indicate a reproach ?)
(= you had no right to be there ?)

b) What did you do in my room? (simple question about a past activity? )

5) a) What were you doing before you came here? (question about a past action in progress?)
b) What did you do before you came here? (= what was your occupation before you
came here ? or Other meaning ?)

6) a) Bill had served in the army for 10 years; then he retired and married. His children were now at school.
(“now” here expresses a time of narration in the past ?)

b) Bill served in the army for 10 years; then he retired and married. His children are now at school.
(“now” here expresses a time of narration in the present ?)

Do you have better explanations, please?

Thank you in advance for your help.
Hela