帮我看看这句英文对不对.定语从句

帮我看看这句英文对不对.定语从句
There's a few people to whom the dictionary is useful.
二楼说的对，people虽是集合名词但表复数概念，谓语动词应该为复数。
但我觉得to放在前面和后面都可以，比如
Mr Jones,for whom I was working ,was very generous about overtime payments.
Mr Johnes,whom I was working for,was very generous about overtime payments.
另外to whom 在定语从句中作什么成分？