Gotchya - The reason I wanted to clarify is because if it is just a case of it causing some insecurity, you might be able to work with it on your end (without asking him). It's very much within the normal spectrum for men to view some pornography and it doesn't at all mean that they are dissatisfied with their relationship.
And, I can see why he would deny it. I don't believe it is necessarily that he's keeping something deep and dark from you, but probably more of a function of being embarrassed. Pornography and masturbation are very personal and having someone confront you about it would probably feel a little mortifying. His first impulse was likely to lie about it because he was skittish and wasn't sure how you would react.
Additionally, lying about one's masturbation habits does not necessarily generalize into other areas of their lives. I personally think that it might be a bit unfair to say that you wouldn't be able to trust him if he doesn't talk about this. Do you discuss every fantasy you've ever had about other men? - This is similar.
Regardless, if you still feel like approaching him about it, I would suggest bringing a fantasy of yours to him and asking him to look/participate with you. Then, after he has seen that you aren't against the idea of fantasy/porn, ask him what turns him on.
Buying a home is a big deal! That would freak anyone out a little! Also, when you start to realize all the little things your partner does that you were previously unaware of - that's a little weird too. It will probably take a while to adjust and to realize that you and he are the same people you were before - there are just more facets.
As for the pornography searches and relating to real life - don't sweat it. His searches probably don't translate at all to what he actually wants (that's why they're fantasies). If he's buying a home with you, I can pretty much assure you that what he wants is you. In fact, you sound like a great girlfriend and he's probably very happy overall. A lot of pornography viewing is curiosity of the unknown, but it doesn't mean that the viewer wants to try it! Introducing new little things into your love life and encouraging the sharing of fantasies may bring more of it out into the open in time. Then again, it may not. He may always harbor a secret fantasy about x,y, or z. But that in no way means he wants to act on it. Also, I suspect that you may have a fantasy or two that you don't want to share, but that you like to think about from time to time - men are often just more visual.
Does this help or comfort you at all?