Congrats on your efforts to date - you are doing well! I will try to answer your questions in the order you listed.
1) You can receiver from a "mini-bonk" by eating simple carbs along with more complex ones - take it easy until you recover.
2) Try to eat about 250 calories an hour - peanut butter sandwich, cliff bars, things of that nature - also, eat a bigger breakfast that has good calories in it - eggs, oatmeal, bacon.
3) At 37 miles already, you will not have any trouble riding the 50 miler come late April - just keep on training, increase some more each week and when the week of the 24th comes around, ride easy leading up to the event and you can make it - fresh legs and the comfort of knowing you put in the miles beforehand.
4) You have come a long way since last year - you will make it - just eat smart, hydrate with water and have fun!