Are the abscesses/bruises in his front or backs?
If he's flat footed, chances are this means he has thin, 'dropped' soles, so would benefit from some protection & support for his feet. Boots &/or pads would be a good idea, to prevent stone bruises/abscesses and provide *comfortable* support/stimulation for his soles. Hoofrehab.com is a great site for more info on hoof function & soundness, including methods of protecting feet while they're not healthy.
I don't know about ithmol. Anything that doesn't kill healthy tissue is good. You can use saline or ACV to just flush out the hole & get rid of germs.
This is his white hoof. His hooves have a tendensy to split- but not seperate. I have had the vet out to do regular maintance and he said white hooves can be softer than his 3 black ones.
The white hoof thing is a myth. The only difference is pigment & that has no capacity for strength. However, his white hoof will tend to allow you to see any problems & bruises more clearly. There may be bruises in the other feet that you can't see. Splitting & chipping, especially in the absence of separation is generally because the walls have become too long & there is unhealthy leverage pressure on them. A split at the toe could have allowed infection in &/or torn into the corium a bit, which may have been the cause of an abscess.
Hoof pics would be good if you would like further advice.