I am so sorry "simple stuff" like this (can't move the dog) just kinda compounds the pain.
13.5 and not eating ... is just not a good combo ... I know you also stated "can't" walk ... but hey that's what doggie wheelchairs are for. But you know the not eating thing ... so yeah ...
But I'm not here to say well that sucks and move on. I'm here to try and help and like I often say to newbies with issues .. " take a deep breath and relax." Your dog needed you those many years ago and he still needs you now. The issue at hand "is getting the dog in the vehical." Step one ... do you have friends, relatives or neighbors that can help you??
Even if you don't know your neighbors well ... (I'm going out on a limb) here and say, "most people" would help someone in trouble with there dog if asked ??? I know I certainly would ... even my butt hole neighbor!
So getting a second set of hands would be most helpful! So "assuming" a second set of hands ... the disadvantage of larger breeds .. is that if they are not mobile ... they are just dead weight! Just the way it is ... no way in heck could I lift "Rocky ... 112 lbs and freaking long ... I'm a "Boxer guy" also.
But ... with a second set of hands ... no problem ... get a sheet fold it in half (length wise) and make a "stretcher" roll the dog into the center of it and with one person on both ends ... you should be able to lift the dog! The tricky part is going to be getting him into the vehical. So "assuming" you can find help ... it would be preferable, if they were at least kinda agile. They will need to get themselves into the vehical while holding the "Stretcher."
And hopefully ... this part is just way overkill but it would not hurt to put Cushions and pillows down in front of the door of the vehical ... just incase someone loses there grip. That's just a "crap happens" contingency.
So again ... sorry you are going through this and lame as it maybe ... maybe this (info) helps?? Keep us posted and God Bless you and your dog ... take care.