Very nice retro design. I am very fond of the A,E,M,N,Z. The tilde is not correct: it can be confused with double acute accent. 10/10

For the tilde, you will need to add a descender stroke in the middle (think like adding an ascending stroke to the left of the circumflex).
The middle stroke will take one square for the lowercase and two for the uppercase.

I can attest to how difficult it is to design decent diacritics with fontstruct at this grid resolution. Valiant of you to attempt it!

My first suggestion is the best, but will take some time. Use the advanced filter setting of 2 x 2 and redistribute most every brick in every letter as they will inevitably scrunch together: a tedious process to be sure. You will gain another notch of control over the placement of the diacritics and have a slightly easier time building a tilde that doesn't look too wide or unbalanced. 2 x 2 filter settings are truly invaluable at this scale for so many reasons.

The second suggestion (which I have highlighted to reveal its construction) relies on brickstacking. This awesome technique can also be time consuming, as you will have to repeat it each time you want such a combination of bricks (you can copy the group of bricks prior to stacking and paste them each time if you decide to use a tilde such as the second suggestion, but you can only copy the “top-most layer” of the stacked bricks themselves). To be honest this semi-obscure method also proves invaluable at this scale and it was for a fontstruction almost precisely these dimensions that inspired me first to figure out exactly how to repeat this once mind-bending and still essential undo bug. After witnessing it twice through no conscious intent of my own but while banging my head against a low-res grid such as this, it slowly revealed itself to me through some concerted if somewhat random spamming of commands. Once I figured it out I couldn’t help but share it. Please stop me, though, from waxing nostalgic for too long, you just wanted to know about how to build a better tilde! :P All I will say is that I am glad I decided to get the technique out way back then, as it is very much other fontstructors who revealed its true usefulness far beyond my own efforts to promote it, then or now! :)