Hi
If he is eating cucumber, he has not totally lost his appetite and he has not lost his need to drink yet; the need to drink is stronger than the need to eat.
Any veg he eats is great and 14 ml is a good session - again, it shows that he hasn't lost his appetite completely. Try to get as much as feed into him as you can - the more you get into him in one session the less often you have to feed. Your aim is to minimise any major weight loss at this stage and help him to fight the bug with his own body reserves as much as possible. You will see when you weigh him again by tomorrow morning whether what you are doing is working, whether you need to dial up or can dial down your support. But you are on the ball straight away, and that is the important thing that is going to make a bit difference since you do not have to play catch up in the first place.
The feeding supprt is there to replace the hay he is not eating, which makes over three quarters of what a piggy is eating in a day and which is what keeps the gut running and stable.
Also try some herbs, lettuce, dandelion and if possible a little fresh grass if you can but introduce it in a just a very small but gradually increasing quantity for the first three days if he is not used to it and needs to ramp up the specialist digestive bacteria first; you do not want to deal with diarrhea on top of everything. Fresh grass is the same fibre as hay but it does often go down a bit better when you are dealing with partial loss of appetite. Start with some feed, then offer grass and fresh veg and finish the session with more feed.
All the best.
Please contact your vet tomorrow re. splitting the dosage. Since none of us is a vet and we can only go by our own experiences, we are not partial to our specific case and the many carefully balanced deliberations that have gone into the dosage.