Boy, thrown in at the deep end, huh??
As for training, you can teach him virtually everything he'll need to know, aside from weightbearing, hard tying(can do serious damage to young growing bodies to pull back or fight against strong force) & high impact exercise. But of course, depends on what he knows now, how much time & experience you have for training, etc. Everything starts with the basics and they to me boil down to respecting your space, yielding to pressure & allowing your touch wherever & with whatever. Develop those things & everything else is pretty much built out of them.
Don't forget hoof care too - he will still need his feet attended every 4-6 weeks on average, but if he's not good for the farrier, it's not their task to teach the horse. I'd concentrate on getting him good about picking up his feet before finding a good farrier also good with training & explain the situation.
As for feed, grass &/or hay is the major need for horses. They need around 2-3%bwt daily in forage & free access or little & often feeding. Low starch/grain/sugar diets are best for providing what else may be needed, such as well balanced nutrition, which is particularly important for a young growing body.
I also feel it's very important to bring a horse up in a relatively natural environment, living & socialising with other horses. Lots of exercise is also beneficial, so if the environment doesn't motivate/allow that, then I would be exercising the horse as much as possible, getting out & about for walks, etc. That also has the benefit of allowing them to experience & be accustomed to a lot of stuff long before 'real' training begins too.