If you haven't been served, you are not restrained. If you have been served with an ex-parte order, you should not respond to Mom's communication under any circumstances and should show up in court to address the RO. Mom's contact with you does not prove her initial report was or was not valid or that you did or did not threaten to kill yourself and threaten her. You have threatened to take the car she uses for transportation from her ON THIS FORUM so apparently you do "say things" when irritated even if you later calm down. It does bring her credibility into question, and this is something you can address if you go to court over the RO.
Your only good option is to see a divorce attorney and attempt to get visitation whenever you have home time. Considering your home time is probably not on a set schedule and you may not have much advance notice as to when you WILL be home, you realistically will need to learn to coparent with Mom. Threatening her, threatening to take the car, threatening anything is not going to help your best interest. Schedule some appointments with attorneys when you are home and go from there. And yes, some OTR drivers do have full custody of their children. But unless you are game to homeschool out of your truck, that isn't a likely scenario here.
And even if you are game to do so, mom has clearly been the primary caretaker and your odds of getting anywhere with that are slim to none.
And unless you are an owner operator, your employer likely would not allow it, and if you are an owner operator your insurance probably would not allow it.
I agree wholeheartedly with St-Kitts. You are not operating from a position of strength here, and making any kinds of threats at all, even if you don't believe that you should be taken seriously, even if you only made them because you are upset, will NOT help you.
Mom however IS operating from a serious position of strength, because she has clearly been the primary caretaker in a situation where a judge honestly could not justify giving primary custody to you.
So, get yourself a consult with a local attorney as soon as you reasonably can, and then be prepared to work with mom and develop a good co-parenting relationship.