I love a graphic t-shirt, but as a short curvy woman, but most graphic t-shirts have a “unisex” fit which has a high crew neckline and long snug sleeves that aren't really my jam. I have mastered no-sew, no measure, no tools needed except a decent pair of scissors way to cut my t-shirts for a more feminine fit.
Do exactly what you did with the sleeves. Turn the t-shirt inside out and cut along the neck band, removing it. This simple modification will instantly open the neckline while still covering bra straps.
At the crossover shoulder to neck seams, cut across it, using the ribbed neck band and not the seaming as your guide. I promise these seams will not unravel even with multiple trips through the washer and dryer.
How the shirt looks after just cutting out the neck band and trimming off the sleeve hems