Hi,
The most important thing for him to have available at all times is hay, this can be timothy, orchard hay, meadow hay or a mixture, so long as it is grass hay and not alfalfa. Alfalfa is not grass, is very high in calcium and does not provide the dietary benefits of grass and so should not be fed.
Pellets are not necessary.
The recommendation for veg is one cup a day but if not feeding pellets this can be increased to 1 1/2 cups a day. It doesn't matter if you feed it all at once or split it up an feed twice (or more) a day. Which ever suits your routine better.
The veg which are safe to feed daily are cucumber, bell pepper (any colour), romaine lettuce and cilantro, so you can give a mixture of these everyday. In addition there are other veg you can give in rotation. A piece of celery can be given 3 or 4 times a week, once a week you can give a slice of apple or carrot, baby corn or a strip of collard greens, or a small amount of other veg you know your piggy likes but do not feed kale, spinach or parsley, all of which are very high in calcium and oxalates.
It is best to avoid all commercial treats as they often contain unsuitable ingredients. If you enjoy hand feeding your piggy treats it would be better to think of pellets as treats and hand feed just one or two a day or better still offer forage as a treat if available such as the odd dandelion leaf or other safe weeds in small amounts.
It is also safe and very good for your piggy to eat fresh grass, so long as they have been introduced slowly.