I have a 17 month old and she's still up 2 to 4 times a night and needs to nurse to settle down to sleep. I don't think there is anything unreasonable about what your baby is doing. Here are some ideas as to why it's more frequent lately:
1: teething or a cold. Is it possible he is cutting some teeth? Drooling, chewing on stuff, clear runny nose, low fever, irritability and clinginess are signs of possible teething. When my DD is teething, she has higher needs to nurse at night and is all around a more restless sleeper. A cold has a similar effect on her nursing behaviour and may be something to consider.
2: growth spurt. Most babies have a pattern of growth spurts they follow but they can happen anytime. Your DS taking 3 large bottles suggests that maybe he is going through one and is likely taking more milk from you at night than usual. His increased nursing frequency also could be his way of increasing your milk supply temporarily to meet his increased needs at the moment.
3: developmental milestone. Babies who are just about to make or have just made a developmental leap often sleep worse as they practice and perfect a new skill. I saw it with rolling over and crawling somewhat, but much more strongly with pulling up and then with walking. Could your DS be on the cusp of a new skill? At these stages nursing is reassuring in a fast changing environment. The world looks completely different to a baby crawling on the floor and a baby standing upright. He could just be looking for extra closeness through this phase.
4: change in routine or environment. Older babies and young toddlers tend to be sensitive to changes in their routine. Moving, house guests, traveling, change of schedule for a parent for example take their toll and LOs need some time to adjust. In the meantime they tend to want more closeness, often including night waking.
5: thirst. Heat waves are hard on babies and BF kids under a year old typically get their fluid from nursing. If it's been particularly hot, baby may simply be more thirsty and need to nurse more at night.
As for the "reliance" on nursing for comfort, it's not an unhealthy thing. He will accept other comforts from dad or grandparents but as long as you maintain your BFing relationship, nursing will be his first choice. It's natural and healthy. It is the one thing uniquely his and yours to share and if he is upset or unwell, it wouldn't make much sense not to nurse him if you're available. As he grows he will rely on it less and less. That is child led weaning. If you plan to nurse him to his second birthday or beyond, then him turning to nursing for comfort is a good thing - one thing that will help prevent abrupt weaning due to circumstances before you both are ready. This is my personal opinion. I just want to reassure you that you're not spoiling him or setting him up for failure by nursing him when he asks. I hope I helped reassure you a little.