Kenfaw

I have recently entered the world of quilting after needlepointing, crocheting and cross stitching for ages. I have been working on my first quilt top and no matter what i do it does not seem I can cut on the exact grain. Many of my strips are shedding thread and as I have sewn them together they do not set square. I used a t-square, cutting mat, rotary cutter, special cutting ruler. Even purchased a mat that already has slits to prevent uneven lines. I washed and starched my fabric, Ironed it, took the tip of pulling it out of the dryer when semi damp and had my partner help me set the threads so the grains would be at 90 degree angles. What did i not do? I even went so far as getting out the magnify glass to make sure the thread were running the way of the ruler. Reading glasses only do so much. Any other suggestions? Even with the 1/4 inch foot on my sewing machine some of the lines to not match up as they 'should'.Second prob silly question, my seams do not lay down flat after pressing. Everything I have read says not to iron just press to avoid stretching. Even after leaving the iron on cotton sitting on the seams they still would rather stand up. Too MUCH Starch? Thanks for any feedback.--Frank