it可以指代整个句子吗？

He gave a little start, and then smiled, but his smile was rueful.

"Why are you idling in this disgraceful fashion?" I asked gaily.

"It's a long time since I was at the Louvre. I thought I'd come and see if they had anything new."

"But you told me you had to get a picture finished this week."

"Strickland's painting in my studio."

"Well?"

"I suggested it myself. He's not strong enough to go back to his own place yet. I thought we could both paint there. Lots of fellows in the Quarter share a studio. I thought it would be fun. I've always thought it would be jolly to have someone to talk to when one was tired of work."

He said all this slowly, detaching statement from statement with a little awkward silence, and he kept his kind, foolish eyes fixed on mine. They were full of tears.

"I don't think I understand," I said.

上面节选中，关于I suggested it myself.中it是指代整个句子Strickland's painting in my studio吗？困惑是：it可否指代整个句子（即整个句子表达了一种意思，然后用it指代，可以吗？），如果用it可指代整个句子，那么与so替代整个句子有什么用法含义差别呢？另外，顺便问一下老师：这里的detaching statement from statement中，为什么可数名词statement可以用零冠词呢？