I'm sorry to hear that Bastien is suddenly needing attention and cuddling at night but he's certainly gotten your attention hasn't he?
It sounds like he is trying to tell us something, unfortunately many problems can cause anxiety so it takes some detective work to figure out exactly what the problem (or problems) is (are).
I know he seems healthy, and his physical examination may be within normal limits, but he may need further diagnostic tests to find the cause.
I would start with a complete blood count, biochemistry profile and T-4.
Hyperthyroidism or an overactive thyroid gland is usually caused by a thyroid gland tumor. It can put cats on edge as they are overstimulated and can make them hungrier as well as it causes a ramped up metabolism where they burn more calories. Both of these things can lead to restless behavior. This can be diagnosed with a blood test.
A sore tooth, gum infections or a mass on the tongue or tonsils can lead to pain and could be the cause of him needing reassurance. During the day when he is distracted he may not be as much aware of his discomfort, but at night when all is quiet he feels it more. He may need sedation by his veterinarian to fully examine his teeth, tonsils and tongue and diagnose these conditions but it won't hurt for you to take a look if he will let you.
Early senility or dementia often causes cats to become more anxious. They are literally begging for attention and reassurance because they are confused and looking for help. This would be very unusual in such a young cat, and it is usually a diagnosis of exclusion meaning that physically everything looks and tests out normal but they are still extremely anxious.
He may be having trouble with his vision and if his sight in dim light is not what it once was that can cause anxiety. So leaving on night-lights to help him see may help. Cats normally see much better than we do, so this might be difficult for you to pick up on during the day when there is lots of light. It would be worth using plug in night lights around the house to see if that helps him see and feel more secure at night.
Perhaps he is bored and not getting enough exercise/attention during the day. It may help to play with him more during the day/evening so he is tired at bedtime and sleeps better. In some cases using music or "white noise" machines to block outside noise is helpful too if outdoor animals are contributing to anxiety.
If his days and nights seem a bit mixed up it may help to give him a supplement called Melatonin. This is a naturally found hormone in animals and people that helps regulate the sleep/wake cycle and is involved in seasonal shedding. It can help them relax and sleep, and in cases that have abnormal shedding patterns related to seasonal light changes or abnormal growth hormone fluctuations. The usual dose in cats is 2mg to 4mg per cat every 12 to 24 hours. Give a dose 2 hours before bedtime. Make sure to read the label and DO NOT use the fast dissolve tablets of Melatonin with xylitol as xylitol is toxic for cats.
We can use calming sprays or diffusors containing Feliway (a synthetic version of a calming pheromone), a homeopathic drop added to his food or water called Rescue Remedy, or a supplement called Zylkene.
If that isn't enough then your veterinarian may prescribe a low dose calming medication like alprazolam.
In short it sounds like your fellow needs a physical examination and minimally some blood tests taken to look for reasons for his behavior. If there isn't a physical cause then we can proceed with altering his environment and using things to reduce anxiety.
Please let me know if you have any questions.