Originally I wasn’t going to chime in because I understand how much work this project is and I didn’t want to really be negative, but since it’s out there now, I have to agree with the others.
You should spend some time looking at the display graphics for Dialed In and Aliens - those are the gold standard for excellent display use. High contrast, Sans serif typefaces, in large formats is your starting point.
You should also consider paying for some good models based on the playfield gophers. Lots of gig economy people can build you 3D models based on 2D art for not a lot of cash.
On the sound, I would recommend using upwork or the other professional voice work sites to get high quality dialog recorded in a proper sound booth. It can be done for less than $300 for everything as most of them are contractors who work from home.
Again, I don’t want to diminish the amazing work this entails. But frankly it lacks polish and doesn’t look professional enough to charge money for right now. As a freeware project? Sure. But you’re asking big bucks.