Hiya, in addition to balanced trimming & nutrition, if you are sure of the mechanics and yet can't get rid of cracks, then they're likely infected. If so, resection & assertive topical treatment is also necessary. While I believe in removing as little wall tissue as possible, it's important to cut back as much as necessary, because wall infection can be very insidious & eat away at healthy tissue faster than it can grow. Good nutrition will also make a horse less susceptible to various infections too, but it doesn't negate the need to treat existing infections assertively.
His hooves still crack, artificially, at the toe when he's in need of a trim(which is every 1-1 1/2 weeks)
Sounds like something's not right there Kyella?? Either his hooves are super weak for some reason & can't bear the slightest strain - in which case being more assertive about relieving them may be one important factor - or you're not being assertive enough at addressing the imbalances, so he's already 'overdue' by only a week or so post trim.