geeme, you basil looks fantastic, the best I have been able to get is sweet basil to raise up about 1 foot, italian bout 8".
I have grown basil and such for 25+ years, as for peppers it is only within the past 10 years that I have been growing chinense variety of peppers, mainly because they just weren't readily available. In the past, ceyenne seed packages, jalepeno and serano could be found. Today, with temporary foreign workers from mexico and filipennes I am finding fresh orange habs, scotch bonnet and for nursery plants hot lemon, habanero and caribbean red. Jalepeno, serano, frenso, anaheim,wax, thai have been available for quite awhile.
But to address the cold issue, yes 0 - 4C(32 - 35F) is dead zone for basil outdoors. Here, let me go look outside at some italian basil I have in a planter, the planter has been covered with a blanket for 3 days as almost everything outside is covered do to cold nights 0C/32F and frost, they are calling for snow tonight but tempuratures should rise back up by thursday(15C/55F)...........bare with me as I run outside to the deck and take a boo, what was a nice green lush basil plant is know a wilted browish figure. I am guessing it is dead, I don't think the day time highs later in the week will have much of a resurrection effect. I have some hearty italian parsley that I should dig up and bring into the house.
To answer some of your other questions, no, the seeds from basil have never survived a winter outside, I have had parsley survive, oregano, thyme and taragon are perennial for me, dill seed comes back every year. Spinach seed comes back everyear. I think the mustard green seeds will survive the winter. (When I reference winter, I am talking -20 to - 35C or -4F to -31F). horseradish survives, mint survives as do my cherry trees. goji also.