I've got a few comments about this; please bear with me.
I have been in a similar situation myself with my 'boyfriend'. It started pissing me off that we never went anywhere and if we did it was never further than the local Wetherspoons for a couple of hours. Booooring.
It started pissing me off that I shopped and paid for the food for the 'nice meal' that I would cook. Boyfriend brought some wine and beer round but it was always just dumped on the table in a carrier bag.
I asked repeatedly for us to go out somewhere, but it never happened because I left him to organise it.
I also think that it's a bit odd for your DP to leave his 14 year old son on his own in his house overnight. That seems tad young to me, if anything were to go wrong.
Why can't you go there, whether the son's home or not?
Why would the son need a babysitter if you went out - he's being left overnight on other occasions.
I also got left with the mess, too. I started asking for help to clean up, and then one day I just thought, 'This is liking having another fucking kid to deal with!!'
At which point I decided boyfriend, despite the 'benefits', was going to be phased out.