Don't read the negative comments and just go with a fitting yourself. Go to a baby shop like Babyjaya in Uptown and just test fit the seats/carriers in your CX5 and buy a suitable sized seat that can secure itself facing backwards (your kid cannot face forward until he/she is able to sit up right on his/her own). Whatever best fits is the best seat for you. All depends on the size of your baby. Find one that has good neck support otherwise buy seat paddings that'll support his/her neck so it doesn't move around.
Are you stupid or something? Modern cars are way more safer than older cars. CX5 has a 5-star NCAP safety rating. Good luck to you and your RM50 car seat. I pity your kid.