Assalamualaikom,
Suhur can be eaten until Fajr prayer.
As stated in the Quran in suraat Al-Bakaraa: and eat and drink, until the white thread of dawn appear to you distinct from its black thread
"Permitted to you, on the night of the fasts, is the approach to your wives. They are your garments and ye are their garments. Allah knoweth what ye used to do secretly among yourselves; but He turned to you and forgave you; so now associate with them, and seek what Allah Hath ordained for you, and eat and drink, until the white thread of dawn appear to you distinct from its black thread; then complete your fast Till the night appears; but do not associate with your wives while ye are in retreat in the mosques. Those are Limits (set by) Allah: Approach not nigh thereto. Thus doth Allah make clear His Signs to men: that they may learn self-restraint."002.187
It is a Sunnah to eat suhur late just before dawn.
Sahih Bukhari Hadith
Hadith no: 144
Narrated / Authority Of: Anas
Zaid bin Thabit said, "We took the Suhur with the Prophet. Then he stood for the prayer." I asked, "What was the interval between the Suhur and the Adhan?" He replied, "The interval was sufficient to recite fifty verses of the Quran."
So you don't have to follow the times in the Ramadan calenders, you just have to finish your suhur before the fajr adhan (call for prayer). Personally, I get up for suhur about 3/4 to 1 hour before adhan, so that I have time to prepare suhur, eat it and then drink water; usually I'm finished about 10 to 15 min. before the adhan.
So to answer your question, yes you can get up at 4.30.
I hope this was helpful.
Salam