Having played through this game a few more times, I've come to the conclusion that I don't really like how the difficulty system is implemented.
I'm not a big fan of how difficulty is implemented in Tlaero & phreaky's games because it seems very artificial to me to have the game arbitrarily end at a certain point due to a metagame decision. However, I understand that some people will want to play at an easier difficulty initially, and it doesn't affect my own playing experience because I always pick Hard.
However, in this game although you need fewer points to progress on the easier levels, you also have fewer opportunities to get those points. For example, during the office section there are about six places to gain extra points on Hard, three on Medium, and none on Easy. That means that having successfully played the game on Easy is no help when trying to play it on Hard, because you've had no chance to learn where the extra scoring opportunities you now need are.
Additionally, the choice of difficulty seems to be the main thing that affects how the story plays out. For example, on Medium difficulty you can't chase after the mystery girl when she passes by the bar, on Hard you can (and on Easy you don't even get to notice her). My personal feeling is that it should be the player in the role of the PC who makes those choices and determines how the story develops, not a metagame decision made at the start of the game. Apart from anything else, having 'difficulty' determine events forces the player to replay the game from the very beginning if they want to see a different outcome. It also makes coding more complicated since you have to constantly test what difficulty the player has selected, as well as produce parallel versions of the same basic scene for each difficulty level. That extra complexity in turn increases the likelihood of bugs and broken links.
I realise it might be a bit late in proceedings to do anything, but my suggestion would be to change the difficulty system to something closer to what Tlaero & phreaky use (ie. where what happens is determined by the player's choices and/or how many points they have) or scrap it entirely.
The difficulty of characterisation in an HTML game is that you don't get much text in which to do it, and most of that text is straight dialogue without inflection or similar metainformation. However, you can do a certain amount of visual characterisation. For instance, what Brad watches on television, how his house is decorated, what he has on his desk, and so on. All those things go towards defining who Brad is and making him seem like a more rounded character. The same applies to the other characters, although the player won't see as much of them. Also, don't be afraid of being specific. For example, what do Brad and Emily actually do for a living? All we're told is that they're business partners, work in the same office, and don't have any employees. That's horribly generic. Telling the player what kind of business it is would increase believability. It's also an opportunity for characterisation, since Brad and Emily are obviously going to be different people if they're lawyers than they would be if they were running a charity for homeless kids (both of which are possible based on the evidence provided).
Re branching storylines, while it's great that the player's decisions have effects downstream, bear in mind that the player only has one savegame slot. In a game of the size this is proposed to be, that could end up forcing the player to replay long stretches of the game just in order to see a different outcome later on. Increasing the number of save slots (if possible) or breaking the game up into parts (if it's possible to transfer variables between parts) might make the game more playable in that respect.
Anyhow, that's just my $0.02.