get a scale that measures at least to 0,01g .. Crystals vary in density so size is very relative

How is SWIY smoking? Maybe the no-breakthrough is due to bad smoking method

As for the bad experience, it could be several things..  Some people feel that low doses are specially negative..  Also was the set and setting good?

Also, maybe a sitter would help, because it would get rid of the preocupation that something bad is happening to you, as there would be someone there making sure you are ok (and that for example your veins arent jumping out of your body  ), so you know that its all just in your head, remember also that DMT is physically very safe, and you can 'let go'  (which is a pre-requisite for having a really good trip)