Need some advice with my cabinet

Hey,
I'm planning on starting a grow in a small space under the roof. Total usable growing area is about 1m * 0.6m, with a height of one meter from the cooltube (with 250w HPS) to the ground.
I still have to add the oscillating fan and a transformator to eliminate fan noise completely, and connect the tube to the vent.

I've never done an indoor grow before, I used to have a nice outdoor location but I moved away from that place :'(
I got a few question before I start growing there:

1. The cabinet is right beneath the roof, and there are some slits where you can feel the air blowing if it's windy outside. My plan is to close these slits, drill a bunch of holes into the board and then use it as a vent. There are no routine infrared scans around here, and the building is so old that nobody would notice a little heat leaking. Do you see any problems with this kind of setup?

2. The doors will serve as air intake, as I don't want to drill any holes from my room to the cabinet. Is there any way to make it airtight without blocking the airflow completely? My idea was to install some kind of mylar curtain on the inside, but I can imagine this would be seriously annoying. Any ideas for a better solution?

3. I don't trust the ceiling to hold the weight of fan and filter, so I just put them on the ground. Are there any disadvantages to that?

4. Lacking proper equipment to attach everything professionally, I used the engineers best friend (ducktape) instead and made sure everything's more or less airtight. I will stresstest the whole thing when it's finished before I start growing, but can it actually happen that ducktape contraptions start leaking when being exposed to warm, humid air all the time?

5. How close can pot grow to a cooltube? It will be around 75 cm from pot to the tube, and I'm planning to use every cm available eventually

6. Last but not least, I would like to hear your opinions to the strains I chose... (didn't order the beans yet)
- 3 Blue Mystic (Nirvana) in the front row
- 3 Fast Haze by AC Genetics (Automatic) in the second row
- 1 Nirvana Northern Lights and Short Rider, leftovers from my last grow as backup
The cabinet probably is a good candidate for a SCROG, but I don't wanna try this until I absolutely know what I'm doing. I'll just tie them down a bit so they don't get too large and hope it all fits
Do you know any other (cheap) strains that would do well in this cab? They should not stink too bad

Thanks in advance, can't wait to get this thing started

edit: I will cover everything in mylar of course

i wouldnt leave thet light attached to the wall like that, your just asking for a fire.

Your cabinet is also going to get quite hot without some sort of air exchange system.

@ Matthebrute: Yeah didn't think about that... I'll insulate the area around the lamp with rockwool or something like that. It is hanging, it's just really close to the ceiling right now. Thanks =)

@ OPM: as I wrote, the air will be vented to the roof.

Honestly if I were you I would be sketched out about growing in there, just get a tent IMO lol

Light too close to ceiling (heat) and no air exchange/blowing outside of room are the two main things that come to mind as well. Also, not sure how hot the cool tube will get but the duct tape might be a problem if it does get quite hot. No problem with the filter being on the ground but it shouldnt really be in the same room. The last few feet in the back wont really be all that useful either (as youve probably realized yourself) since the ceiling is too low. Have you thought about how you will water the plants that are in the back? You should be able to have the light very close to the plants with "just" a 250w and a cooltube. I had my plants maybe within a foot of a 400w HPS without a cooltube.