Hi there. Sorry to hear you are feeling frustrated with your meal times.
I consider self feeding and using cutlery as two distinctly separate skills. One involves getting food in their own mouth (by any means) the other involves learning to use tools. My DS has self fed since 6 months, he was also introduced to a fork shortly after, maybe 6 or 7 months, and has gradually learned to use all his cutlery (knife, fork spoon) however he is now 3 and still chooses to eat with his fingers depending on the food or how he feels that day. I see no problem in it, tool use is quite difficult to master.
It sounds like he is exhausted from his new nursery experience and from his illness so I would just make sure he gets plenty of fluids just now and whatever solids he is willing to take. When he is feeling better his appetite should pick up and he'll likely make up for the lost calories and eat your fridge clean. During his illness I would likely serve up mashed food if that's what he wants during illness, we all eat selectively when we are poorly, well I do.
Once he is better I would totally step back and put way less focus on spoon use. Serve his meal, provide a spoon or fork (forks are easier as the food doesn't fall off after stabbing) and leave him to it. If he uses his fingers to eat, fine, if he uses the fork or spoon fine. If he'd like you to pre-load a fork with some food then fine (only do it if it isn't going to frustrate you though). I used to pre-load the fork then put it down so LO could pick it up himself.
Does he have a range of foods he likes? If so you can serve up any of them and he can eat with his fingers (soup can be drunk from a bowl or cup) whilst you eat your meal, free from stress, enjoy it. Watching you enjoy your food and use your cutlery will be positive modelling for him and cutting out the stresses and frustrations will help everyone enjoy family meal times together. Make conversation about something other than his cutlery, normal chit chat.
hth
