Feel as if/ feel as

park sang joonI'd like to know what is the difference between #1 and #2 in the meaning.

#1 is questionable grammar: 'were', not 'was', is required there in strict English.
#2 is meaningless; it is not a possible English construction.

On the other hand, this is fine:

He felt that Jane was mad at him.

Thank you, Mr. Micawber, for your so very kind answer.

#1 is questionable grammar: 'were', not 'was', is required there in strict English.

I meant conditional 1, not conditional 2

#2 is meaningless; it is not a possible English construction.

He felt as one does in a serious illness when the vitality is so low that one

park sang joonI meant conditional 1, not conditional 2

But you constructed a mixed conditional instead. Conditional 1 (if 'as if' is an actual conditional) would be: 'he feels as if she is...'

park sang joonHe felt as one does.. . Then I was wondering why "feel as" is used here.

It may have something to with the dummy verb

Thank you, Mr. Micawber, for your continuing support.

He was surprised at himself because he ceased to believe *** so easi

park sang joonThen I'd also like to know if "did" indicates "felt", not "ceased to believe ***" here.

That's right.