Emily, it sounds like your boyfriend is perhaps from a culture of tight-knit families where academic achievement and social standing is very important to them?
That is to say that your boyfriends' family might not have been going out of their way to be specifically rude, its just they cannot perhaps help who they are? This may also go some way to explaining your partners out-of-character erratic behaviour. If his father is ill it can be a lot to deal with.
If it sounds like I am defending his actions I am not. Clearly they hurt your feelings and it should not happen again. You should not however have to compromise yourself to fit their ideals. You should stay true to yourself and your own values. This is the most important thing. Above all don't fall into the pit of comparing yourself to others; everyone measures their progress by a different yardstick.
It sounds like your boyfriend loves you very much and is willing to stand up for you. This can only ever be a good sign as he clearly sees you as his number one priority. You wouldn't be the first person to have friction with their in-laws :) Its great you see a future together.
Talk things through with your partner. Tell him how you feel. Burying and bottling things up will only make things worse. He clearly loves you a great deal. Map out your future together. Three years together would indicate you share the same goals. Will you both move or settle elsewhere? Will you only have to bear the in-laws at the holidays or are they expecting a weekly meal?
It sounds like what you have is worth holding on to. I've been married to a wonderful woman for nearly 20 years now. We've had our ups and downs as any couple does but we always talk things through together.