Well, "all over the opening after achieving erection" sounds quite a reasonable description.

When you try to retract with an erection, it will generally look
something like this - there is an edge which is the tight band all round, preventing further retraction. That edge is where you need to apply the cream, nowhere else and it is probably preferable not to get it on the glans. When you pull it back like that, most of the "edge" will end up on the outside.
The "balloon" trick is to determine whether there are any remaining attachments of the glans proper to the foreskin - there probably are not in your case, and the part you are holding closed will be the tight band anyway, so you are looking at different things. If it looks like a nice little "balloon" and is completely concealing the glans, then there are no adhesions of any concern. If (apart from the frænulum on the underneath,) there are any pieces of the balloon "missing", then you might have an adhesion.
I think it is very apt that you say "it felt like my penis is going to explode when someone else touched it" because there is nothing
wrong with that - it is entirely to be expected. Clearly
you, being the owner of the penis, know exactly how much pressure and not too much, to use to make it pleasurable. A young lady who does not possess a penis, really has no idea - any more than you would of how to handle her clitoris, which is
normally every bit as sensitive as your protected glans - because hers is protected also.
Even if she
had experience with penes before, this may have been with circumcised men, who are nowhere near as sensitive, or with intact men whose foreskin retracts easily. If she then attempts to pull your foreskin back and/ or suck on your glans as if it was one of these, she probably expects it to go back easily and you to be less sensitive. The problem is not
yours, it's
her lack of familiarity and care. You can't expect her to know all about you, and I wonder how you might have fared stroking or tonguing her?
In fact, you probably
could have had intercourse (if that was appropriate, and without a condom, I would say it would not be) -
if she was sufficiently lubricated for it to happen - which is something you will see I have discussed frequently here before.