Since + to be(part 3)?

Hi, dear teachers. This is the last part. The following sentences are rewritten versions of those I have read on fraze.it. Would you please check my interpretations?

1. The whole thing has changed since I was in the workforce.

I think it means "the whole thing has changed since I left the workforce". Right?

2. The whole thing has changed since he was in the workforce.

I think it still means "the whole thing has changed since he left the workforce". Right?

3. Alice has written to Peter frequently since she was ill.

I think this sentence is wrong. Right?

4. Alice has written to Peter frequently since he was ill.

I think it means "Alice has written to Peter frequently after he recovered from illness". Right?

5. She hasn't written to me frequently since I was ill.

I think it means "The last time she wrote to me was at some time during the time I was still ill". Right?

6. Jason Jeralds, owner of the Tustin Brewing Company, has known Bone since he was on the planning commission in the mid-'90s.

I find this sentence is interesting. If the "he" refers to Jason, then this sentence means "Jason has known Bone since Jason became a member of the planning commission". If the "he" refers to Bone, then the sentence means "Jason has known Bone since Bone quit the planning commission". Am I right?

7. Jason has known Bone since he was at school.

Likewise, sentence 7 can be interpreted in two ways. If "he" refers to Jason, then it means "Jason has known Bone since Jason began to attend school regularly". If "he" refers to "Bone", then it means "Jason has known Bone since Bone graduated from school". Am I right?

8. Jason hasn't cooperated with Bone since he was on the planning commission.

I think no matter who "he" refers to, the sentence means "The last time Jason cooperated with Bone was at some time during the time when he was still on the planning commission".

Would you please check my interpretations? Thank you very much.