Reread again with an open mind and you'll see that TJ is always in Ian's mind and heart.
The ONLY reason he decided to go with Jo because the latter insisted. But he immediately turnaround and asked TJ to go with him instead. AFTER Jo had asked.
That itself tells you everything. I never understand how ppl cannot see it.
Like the moment TJ dropped the gang, you know Ian is going with his man. Because that's what he wanted from the start. TJ sans the gang.

i dont know how to feel. i was really rooting for ian to finally move on and start the life he deserved.. and i felt like it couldve been so great with jo. it just felt like the story was leading up to him and joseph and then all of a sudden it was a last minute dump and he ends up with tj. i just dont understand. i read everything in basically one sitting though so its a lot to process. but i just dont like how this ended.. call it bittersweet but in my heart i think he shouldve ended up with jo or maybe just none of them.