I've been taking practice exams and skipping the writing part and just jumping right into the quant section. Is this a bad idea? I feel like my attention span is not getting practice for what's to come on test day. I would be appreciative if anyone could help me out. thanks

Yeah, it's a bad idea. The essays come first and you will have to do them on test day, so you want to make sure you get used to doing them in practice. Stamina is definitely an issue - if you don't do the essays on practice exams, you will find yourself a lot more tired towards the end of the real test and not able to perform as well.