Reading your post does bring so many thoughts rushing to my head, the firsts of everything are so hard. First time away on your own, first birthday, first conflict, first screw up by a service provider and I hate to say it that list will go on with the passage of time. However ... every one can make you stronger and every one has to be worked through, friends and family will be there to support you just as they were for me. There will be times when you just want to scream at someone or cry big tears that are from frustration as well as grief.
One huge mistake I made was trying to deal with my grief alone, It took a very special friend to actually point out to me that I was not dealing with it at all,I was just trying to brush it all to one side and hope it would go away.
I went for one to one counselling arranged through the hospice, it wasn't all about my loss it was as much about finding myself and starting my life over again a little at a time.
Things do get easier and,if you let them, things can get better. For me a lot of it was about regaining my confidence. You sound as though you are already making big strides in the right direction there.
Take the advice from others here about the potential new neighbour, it is sound advice and you really do not need some idiot harassing you at any time, but especially not now.
Of course you miss David, but as you deal with every "first" then gradually you will grow more confident the memories will turn into things that give you great comfort, the pain is still there but it starts to hurt less.
You are doing really well, if ever you need to chat please just PM me.
Thinking of you as always