Hi Applestrudz,
You are very most welcome. Just like to offer my advices and help
to those in need.
Like I mentioned before, in a relationship or on issues of emotion
or feelings, there is no right or wrong, so there is no "fault" on
either sides, it is just an issue of suitability between 2 parties.
However, I just like to clarify that there may be some issues in a
relationship that people will classified under the "right or wrong"
category, but that may be off the topic.
Since there is no "fault" on both sides, so as a man, he wouldn't
be expecting any apologies from you and you should be open-minded
and with an open heart not expect an apology from him. Like you
said, the only "fault" is that there was a mis-match in
expectations. In my view, the "faults" also include
miscommunication and also misunderstanding.
On the topic of expectation, I like to point out one thing. You
see, there are many levels of friendship and people tends to have
different expectation for each level. When a person ask his/her
friend to do something, if this friend could not fulfil the task,
the person in turn will NOT feel disappointed because the level of
expectation is not there. However, for a special or close friend,
when he/she could not complete the task, we will be quite
disappointed because of the level of expectation set there. So goes
the saying, the higher the expectation, the harder the fall.
Expectation and anticipation can be common pitfalls in a
relationship, however, it is also because of these 2 factors that
make a relationship interesting and motivating. The key is in not
setting too high or too low a standard but just right. It is also
because of expectation that we can understand better of one's
ablility and limitation and accept that person truly as who he/she
is.
Enough of that, back to the topic. Like I say, don't anticipate too
much, maybe you are still his 1st priority but he is just
suppressing his emotion and masking it up with his work. Or maybe
he had to prioritize his work due to a coming deadline. You are
still enjoying that "privilege" because didn't he did a good job
with your materials when you ask for his help. 
Since you are going overseas, use that as an opportunity to give
him a treat, say as to thank him for his help with your materials
and after that, go for a coffee session to do some catching up
which he had suggested earlier. Like-wise, you can do some
catching-up after your return so that you can share your overseas
trip experience with him.
As you mentioned in your last post, you are those passive type,
that can explain quite a lot of things as you are those "bei dong"
or those who will be move. For the active type, they are the "zhu
dong" or those who will make the move. So that can explain why you
are not making the first move. However, there is no harm in making
the first move. Don't think or anticipate too much, take one step
at a time. He had already make a first small move, now, you should
see when the opportunity comes and make the next move.
Don't be confuse, rationale is your mind telling you the decision
to be made, emotional is your heart telling you what you want to
do. Be bold, pluck up your courage, I believe a lot of your friends
and even family members will stand behind you to give you the
support.
Whatever is your decision or move, I wish you all the very best.
Good luck 
PS : Sorry for such a long post. I will be overseas for a week
prior returning to the homeland, so, just like to offer what I can.
I wish you the best of luck. Good luck. 