I think the phrase construction is not ideal. Look up the subjunctive form:
You should help John rather than he help you.
Using the progressive form, which suggests the action is ongoing, is an alternative way to express the same concept:
You should be helping John instead of him helping you.
From Lexico (formerly Oxford Dictionaries)
- In that-clauses
Nowadays it [the subjunctive] is probably most frequent in that-clauses with verbs such as demand, insist, pray, recommend, suggest, and semantically related nouns/adjectives, e.g. essential, important, insistence, proposal, etc.
- She declined a seat beside Charles on the sofa. She insisted that Jane sit there.
- It was suggested that he wait until the next morning.
- It is important that they be aware of the provisions of the Act.
Note: In most such cases it can be replaced by should + infinitive or by the indicative form of the verb:
- She declined a seat beside Charles on the sofa. She insisted that Jane sat there.
- It was suggested that he should wait until the next morning.