yeah the SGFC has a grid of holes in it, there's many tutorials on how to make it.. the style you made is more close to a monotub, which is a tub with few but bigger holes filled with polyfil or covered with micropore tape(like you did), the design you made might be good but it's better to follow the proven and tried methods..
the moment the cake is birthed and comes in contact with air all sorts of contaminants land on it, the purpose of the micropore or the polyfil(in fruiting chambers) is not to filter the air but to regulate the air exchange and hold the moisture otherwise the cake will dry up fast.. in the case of SGFC bcz the holes are small and the presence of wet perlite, this creates the balance between humidity and FAE so there's no need to cover the holes..
about contamination there's a lot of misconception, i'll try too explain a bit..
once the mycelium colonizes all the nutrition and is healthy, it's very unlikely that it will get contaminated even if exposed to contaminants(which always happens since you expose it to open air), the mycelium can defend itself and if there is no uncolonized parts the contaminants have no place to strike.. after several flushes and as the mycelium weakens it becomes more prone to contamination. in most cases of contamination, the contaminant is already in the spawn, the cake doesn't catch it in the fruiting stage but already has it.
so from the moment of fruiting and after there is no need to be extra clean, bcz the cakes already have contaminants all over them and you can do nothing about it.
however there is certain infections that can happen if the FAE is low or some other bad conditions.. if the mushrooms stay wet for too long they become infected with bacteria.
like i said passive fresh air exchange is better, a fan is not a good idea, the holes you made are not ideal compared to how the holes are in a monotub but they are big and seem good, you can make two smaller holes on the other sides but make them at cake level and cover them with micropore too
yes it takes around 7 days and up to 10 for pins to mature but their growth is not linear, first few days they grow little last 2 days they explode