The Intel HD 3000 is oollldd, that is your primary bottleneck more than anything else you’ve said/listed. There are even threads specifically about that video ‘card’ on the unreal forums (generally it was disabled for Mac for a while, dunno if it’s not now) but even the 4200 (directly mentioned in another thread, on answerhub) is below the minimum specs listed by Epic.
You need a new video card, the one you have is not going to have its performance improved dramatically, it’s very old (tech) and very underpowered. Otherwise you’re basically going to be developing for mobile (quality wise) or dealing with possibly single digit FPS in the editor.