Hi, Lintama, I don't think that you will over do it if you give it some 'miracle grow' as well as the bone meal, especially at this time of year, I always advise my customers to feed until the end of July, then no more , to give the plants chance to toughen up a bit before the winter, but this winter even that would not have helped, as down here in West Cornwall we had the coldest spell for about 24 years with temperature down to -12 C and even -15 C near Penzance where it did an enormous amount of dammage. It will obviously do a lot better in the open ground, because the pot, no matter how big will have a 'bonsai' effect on the plant, but if you feed every couple of weeks until the end of July and give one or two doses of Dithane 924 per season it should thrive (and eventually flower)
Best wishes lannerman