cg,
i think u definitely need to switch the cinnamon to casia.
i particularly like star anis and use it all the time even for pre cooking chicken.
i found an earlier post (
https://curry-recipes.co.uk/curry/index.php/topic,2454.msg21350.html#msg21350) on frying whole very helpful - ie roast each spice individually
on the use of other spice to make garam i think the more the better (i currently use 13).
nb i no longer make my own curry powder having recently succumbed to trying the rajah - it was really top notch and much better than i could make myself (much closer to BIR). i am also going to buy the rajah garam to compare against my own. in short diy roasting is good to get an understanding of the taste of the individual spices but it may not get close enough to BIR.