very interesting when you talk about not tollerating the acids. i used to get GABA for 9 months. my doc went slowly from 100mgs to 300mgs and did not do much of anything. so i decided to stop 1.5 months ago. i think that from then my stomach became more sensitive to acids and it gives me often the pukeing sensation. do you think it s because i stopped?
700/750mgs sounds to me a lot but i wonder if it would make me feel better if i try it...
Lemme think...: A "puking sensation", nausea, can come from acid reflux/GERD. Not only from hyperacidity, also from hypoacidity (praps your stomach got used to the acid over the 9 months, reduced and became hypoacidic after you left it, then your stomach overcompensates with too much). If you search for <nausea stop gaba> you will find: "A sudden stop in taking GABA may cause withdrawal symptoms such as headaches, nausea, diarrhea, insomnia, and seizures." 9 months habituation could explain the 1.5+ months nausea.
Looking for <Natural Relief for Acid Reflux Due to Hypoacidity> can help you find ideas. In short: chew more, drink more, but not with meals, decrease raw food, incl. fruit, dairy, meat, sugar, gluten; try apple cider vinegar before or to meals, 15' walk after eating, probiotics. (Trudy Scott recommends going down on gluten/sugar/caffeine anyway.)
Trudy Scott recommends starting with 100-200mg and building up to 1000mg inside of a few
weeks according to the improvement of the symptoms. GABA is not something you need to get used to, you will know pretty quick. If you need it, the symptoms will getter the more you take, until you pass the right point, then the symptoms will start getting worse again. That's the way my colleague did it recently, 125mg wasn't enough, she increased and realized more than 300mg is too much, so that's her optimum.
I haven't reached my optimum yet, due to not tolerating it sublingually, so now I've started with capsules and additional supps to keep the acid down, I can increase again, I'm at 1000mg (650+350+x) without acid problems, so I can increase further.
As it is influencing your acid balance I'd try the 'natural relief' recommended above to get it balanced first, then start again with the 300mg or more you left off (that way you will quickly feel the GI-side effects if they are there and can see if your body gets used to it or do something about it).
Maximum is about 2000mg, 2g, so 750mg is not really a lot: Most products I see have that, that's why I bought it, so it seems normal.
However now knowing about the whole group of amino acids, I'd look at Trudy Scott's <Amino Acids Mood Questionnaire> first, to get a feeling if it really is a low GABA problem, seeing as it didn't work at all. It might for instance be low serotonin, instead or aswell, which'd mean using tryptophan or 5-HTP (additionally), or tyrosine for low catecholamines (dopamine) etc.
One reason why I was pretty sure GABA might help - without knowing of all this - was reading that it reduces muscle tone and excitability, which fits very much. The colleague mentioned above said the same, whilst my acupressurist did not, she just thought as we have similar problems maybe it'd help her. After me giving her the book to read (German translation), she realized it's tyrosine she probably needs, be interesting to hear next week what experiences she's making...
It's more important for me to do anything re. all I do than do some Asian style perfectly, even tho it doesn't fit to me. I know, I'm so totally boorish that way... 
