That makes sense.
I just wanted to make sure you understand that I wasn't trying to make you change the hardware store. That's a good location for the story. I was just trying to suggest one possibility in case the hardware store was part of your writers block.
I have a few more suggestions. The first is, you said that Simon is one of the lead characters. You may have been trying to make it short and concise, but you didn't mention him in your synopsis until the last sentance. If in your head, he's not already introduced earlier in the story, then try thinking about introducing him earlier. For him to be a lead, the audience will have to know a lot about him, possibly seeing some events that are just him. And you may (not always, as standards are made to be broken!) want to introduce him almost as soon as you introduce Daniel (something like the movie starts out watching Daniel in his house and Simon comes over to hang out or something along those lines of introducing them as friends early as well?).
My second suggestion is, and you probably already know this, is that there are general distances that you often see between characters based on their relationship. (I'm just doing this off the top of my head so it might not be completely accurate) Acquaintences (sp?) 'generally' stand about 4 feet or more away from each other. Friends are between 4 feet and 1-2 feet, two people who are really good friends/very close would be 1-2 feet to 6 inches. And Intimate is 6 inches or less. (Keep in mind I'm not sure those are the generalities, and that it's nothing meant to be set in stone, just suggestions for character placement... ultimately put the characters where it 'feels' right). You could try to think of how Daniel/John or Daniel/Simon would react if they were in a really close distance (closer than you originally imagined). That might open up new character traits, scenes, developments in the story. Of course, you could do the opposite as well, and think how they would act being really far apart.
As far as the themes, a love/friendship theme could work really well with a not belonging theme. Make the themes contrast themselves, by having Daniel feel 'normal' and fit in really well (like say 'the right' things and such) when he is with John and/or Simon. Make him a bit more nervous around other people (and possibly after things develop when he is around John and Simon at the same time) and have him not always say 'the right' thing.
It sounds to me like the film will be very character driven rather than plot driven. Those are often the tougher ones to write (hence why 90+% of Hollywood is plot driven). If all else fails, try this: do your best to define what kind of characteristics you want your characters to have. Then, take a look at events in your day (for example, something simple like a really long line at the grocery store), and think how these characters, based on their characteristics (which by no means have to be set in stone), would react in those situations. How would Daniel alone handle it? How would Daniel and Simon handle it together? In doing that, you might be able to come up with some interesting ways the characters interact and you can then mold those situations into the kinds of situations you want in your film
Hope this helps!