I agree, you need to sit down and talk this through with your dp. Interfaith relationships can & do work - I've been in one for 16 years, and still going strong! But open, honest communication is a must.
You need to accept that his family may never approve of your relationship. If you get married and have kids, they may even cut you off completely and have no contact - I know a family in this position, grandparents have never even met the grandchildren, despite living down the road. Could you cope if that happened? Could he?
What if they remained in contact but constantly expressed their disapproval. Would he fight back? Would he cut off contact with them? Or would he roll over & play dead? How would you cope in these scenarios?
As for your own relationship, you say that he doesn't want you to change in any way, or convert to Islam. Fair enough, but would he want your children raised as Muslims, and if so, would you be ok with that? What would that mean for them in practice, as they are growing up? Would they be able to celebrate Christmas, for example? Would they be allowed to date as teenagers? Etc etc. You also need to think about what all this might mean for your own child - how would all this affect him?
I think you need to bear in mind the fact that religious belief & practice are not static and unchanging. As people get older, their views change over time. It's not unusual, for example, for someone's convictions to fade over time, but in other cases, people often return later in life to the stricter interpretations of faith from their childhoods. If your dp became more devout in his beliefs over time, how might that impact on you? How would it impact on him at a later date if you suddenly started practicing Christianity? How would any such changes impact on children?
The race issue is difficult and the prejudices probably won't go away. If you have children, they would be mixed race, and it's possible that they might be rejected by his family for that reason. Are you both strong enough to deal with that, to give them the self-esteem so that they can deal with it?
To some extent, I understand his fear of telling his dad about you. Filial obedience & respect for parents is prized very highly in some Asian cultures, and that isn't necessarily a bad thing - I love the way my DH respects and values my parents for example. But ultimately, you need to know who he'd choose if he were forced to make a choice. Ask him!
Good luck!