Sulcata, especially young ones, need a varied diet. One that is high in fiber, meaning grasses and weeds. Kale and lettuce are not bad foods, unless they are all that is being fed. This thread, and there are others in the top of the Sulcata section of the forum, give a good explanation of their dietary needs. http://www.tortoiseforum.org/threads/for-those-who-have-a-young-sulcata.76744/
Ideally, grass and hay. Safe weeds from your yard.
Too much kale can block calcium absorption. It can be fed, but only in slight moderation as part of a varied diet. Most lettuce simply lacks the nutrients out tortoises need.
Just so there's no confusion on anyone who reads this thread - a sulcata is sometimes referred to as 'African spurred tortoise,' while the Greek species of tortoises is called a 'spur thigh.'
You can get him orchard grass pellets from some place like Tractor Supply just soak them and you are good to go. Add weeds and check the list from above.