Could you please clarify the difference between 'them' and which one of them sounds more natural?

1) He lavishes as much love and care on his dog as he does on his wife.

2He lavishes love and care on his dog as much as he does on his wife.

3) He lavishes as much love and care for his dog as his wife.

Question

Could you please clarify the difference between 'them' and which one of them sounds more natural?

1) He lavishes as much love and care on his dog as he does on his wife.

2He lavishes love and care on his dog as much as he does on his wife.

3) He lavishes as much love and care for his dog as his wife.

Answer

#1 and #2 are excellent and mean the same. #3 is also OK, and means the same, but it is customary to use "on" rather than "for". The models to keep in mind are:

Lavish SOMEBODY with SOMETHING
Lavish SOMETHING on SOMETHING

You could redo #3 as:
"He lavishes his dog with as much love as he does his wife."