What do you get out of this?. From reading this so very little and most of the time you're not together anyway so you are on your own. There are good reasons why this has been on and off for 18 months and that is also because you and he are fundamentally incompatible.
Re your comment:-
"I don't know if I'm just in some kind of denial that it will get better once we can go out and about a bit more".
That reads like the sunk costs fallacy and that basically causes people to keep on making poor relationship decisions. Its not working so stop chucking more time and resources at it, these costs are sunk ones and will not be recouped.
People get bogged down by focusing on their sunk costs.
There are two ways to understand this process, both involving avoidance. One is an avoidance of disappointment or loss when something doesn’t work out. When a relationship doesn’t succeed, especially after a long period, especially after many shared experiences and especially after developing a hope that the relationship would be a good one, it is a loss. It is a loss of what might have been and an acknowledgement that a part of one’s life has been devoted to this endeavour.
Another angle to evaluate is that focus on “sunk cost” creates a distraction from one’s inner truth. The sentence often goes like, “I’ve already invested so much, so I can’t notice my thoughts and feelings that are telling me to end or change this relationship.”
This is a type of insidious defense against noticing yourself. You enter into a neglectful relationship with yourself which divorces you from your inner thoughts and the quiet feelings that might guide you in your life. In other words, thinking about what already has been may prevent you from deciding what you want your life to be.
It is indeed better to be on your own than to be so badly accompanied.