Sup man, having had a well built obby mauler pure in the past and currently building an obby tank right now (legitly) I'll give you some advice;
By looks of it you're already considering 60 attack, if you're considering it this early on then you've got no chance when it comes to the slayer staff grind of achieving 55 slayer without being range/mage base, yes thats 220-260 Tureal slayer tasks which are all farely easy just long and low exp, reason for Tureal is because all tasks can be mauled and he's the Slayer master you can use right off the bat (Vanakka is cmb 40)
As far as training goes rock crabs is and always will be your friend on this particular build, hit low and low defence for you to pummle through with such a low attack level, alternativly you could try Flesh Crawlers however take food and best armour set up possible.