for the 5, maybe a bigger jump so you have more time, but if you can get the body around the skis should just follow, make sure you kick your skis around when you get to it
now to grabbing 3's, the reason why you stop spinning is because when you grab, you look for the ski, and if im thinkin of what your doing right, you are grabbing with the opposite hand to what way you are skiing (ex. spin left, grab with right hand), if this is the case then maybe try ur other hand or just make sure when you are lookin for the grab to keep ur other arm rotated around your body so you keep spinning and you are pushing your body that way, and once you have to the grab to look for the landing
if its not the case and you are grabbing with the same hand to the side you are spinning (ex. left hand and spinning to the left) then theres nuthin really different to it then a regular spin except you dont have ur arm to help bring urself around, just turn ur body and look for ur landing and it should work out for you
i suggest just grabbing under ur boot with the same ski as what hand you will grab, and use the hand that is to the side you are spinning, that way its more balanced for you, and you dont take a lot of time looking for the grab, you dont even have to look for it, its just right there, not hard to miss, and then once you've got that down move to other grabs more towards your tail or nose and maybe try the other hand