1、It’s difficult choosing the right candidate and I want to be sure that both the company and the employee will benefit from one another.这里的It’s difficult doing 结构对不对，我记得常用的是It’s difficult to do 的结构，请问这两者有什么区别？这里能不能改为后者？

1、When I was a student I was broke, so I took a part-time job to help support myself.我觉得在语法上这里的help好像有点多余，请问这个help可不可以去掉，或者加在这里有什么作用？

应该是difficult to do
+doing 的我还没见过


用help的原因是因为他自己无法支付全部的抚养费,兼职只能赚到部分而已,所以可能是减轻家里的负担等经济来源.
如果用了help的话,support 就应该作为名词."维持生计,抚养;生活费"
所以个人觉得应该是help support of myself.
去掉help 也可以,但是句子意思会发生变化.

很感谢你的解答.
第一句我也觉得应该是difficult to do，至于第二句你解释的help的作用很有道理，这样一来support是应该为名词，我也赞同你的看法，但既然这样，我可不可以把support改为supporting呢，即help supporting myself？

sentence 1, Kobe is right. "difficult to do" but "have difficult (in) doing"
sentence 2, "help support" is necessary. You can't delete "help" in this sentence. Because if you delete it, the sentence means you have no other supporting methods, you are living on p-t job.  As for grammar, you may add 'to' after 'help', you may not. Either is OK. And 'support' here is not a noun, it's a verb.