One person can not follow two or more religions at the same time. By following religion I mean that you do your nitnem everyday. and try to follow the panthic rehat maryada. If you really know all these religions than you know for a fact that you can't follow all of them at the same time. You can't have one foot in one boat and other foot in another boat. An amritdhari cant be worshiping idol like in Hinduism and Christianity. That is what he meant by hodge podge. the kids are usually confused and can't really commit to one religion. it does happen but its every rare when both parents accept one religion. I have seen it happen but rare.
You can wear the necklace that has a kirpan and kanga. For the kacherra you can try to make a small one that clings to your body more. If not just do a rdas before and after riding your bike that youre taking off your kakar and please forgive me