I took over hand feeding my jenday Alex when he was on 3 feeds a day, morning noon and night. But, I was taught how to handfeed over the course of a few weeks by his breeder, and only took him as she was ill and had to be hospitalised. Wanting to hand-rear your own birds is not a bad thing like we seem to make it out to be, but attempting it without knowing what to do is. You should have been taught how to by the breeder, not given a 'crash course' when you took the chick. If you are unsure of how to do things now, she has not taught you properly.
In all honesty you should ask a local breeder to raise this chick for you, some will do it for a minimal fee. You've bought a life without the necessary training to ensure it flourishes.
I'm not saying you can't do it, but it's time to learn NOW and FAST if you want to do this. So, as you've said your not willing to transfer the chick to someone with more experience, lets get down to business. Everyone here has already given you very sound advice, so I'll throw in my own experience.
Are you using a spoon or syringe? If using a syringe do you know how to feed with it? You can easily asphyxiate the chick by accidentally getting food in it's windpipe and as a result, lungs. If you can't get a breeder to teach you how in person, your next best bet is to youtube up some videos and watch how it it done. It's no where near as good as having someone show you and supervise you doing it to correct you where you go wrong, but, it will have to suffice. I used a spoon as I was not comfortable with a syringe, but Alex had (and still has) a much larger and therefore easier to spoon feed beak, then a baby lovebird.
You are going to need a thermometer, formula needs to be the correct temp, especially at this age! Too low and your risking bacterial infections in the crop, too high and you will burn the chicks crop killing it. It's a very precise range. Like everyone said, candy thermometers, meat thermometers or sometimes you can find digital thermometers designed for use in heating milk for children that may work, that is what I used.
Next is heating the formula itself. Avoid a microwave, you are just asking for trouble, and at least if using boiled water you know it is sterile. Their are different methods of mixing it up. I personally would boil the kettle, mix the boiled water with the formula to the desired consistency (a yoghurt like thickness worked best for me and Alex) and stir it while waiting for it to cool to the desired temp. Once it was at feeding temp, stir it thoroughly to make sure their are no lumps and the heat is distributed evenly, and feed immediately. You can sit the container with the formula in it in another bowl of warm water to keep the temp stable longer.
Your going to need to learn what a full and empty crop looks like. Sometimes it can be half full, sometimes less. Here's a CAG with a full crop for an idea.
The big round bit is a nice full crop.
Also research signs of slow crop and bacterial infections so you can pick up on them FAST if they show up.
A chick at this age needs to be in a brooder IMHO. It should NOT have been pulled from the nest if it was not to be placed in a brooder. If you can post some photos so we can see how feathered he is and how far along developmental wise, it would help.
I would be personally feeding this chick
whenever it is hungry at this stage. It's crop is emptying so fast because it is trying to keep itself warm, using all the energy in the food to try to do so. Feeding it once every 12 hours is nowhere near enough! Alex was on 3 feeds a day when I got him at 9 weeks! From what I hear, you should let the chicks crop empty out once a day to prevent bacterial infections, but let the others confirm/deny that.
Basicly, if you really want to do this, research NOW and get the right stuff and doing this right NOW or otherwise you're going to have a dead chick like almost everyone else who trys to "wing it" through hand rearing a bird. I'm wishing you the best of luck, and hoping you can do it, but you need to do it right, or not at all and get this bird to someone who will.