You need a bike that is going to be reliable and which is easy and cheap to look after/maintain and keep roadworthy. Other than that, as long as it fits you and is reasonably comfortable, everything else is just detail. Don't get hung up on detail - most of the bikes you will be looking at will probably do. It's not the case that one bike will be fantastically better than all the others and will make a decisive difference to whether you succeed. I know you want to feel you've got the best tool for the job, but ultimately it's your attitude, determination and willpower that will be decisive. Not the bike.
That said, I would make the following comments:
1. The difference between a freewheel and a freehub/cassette is explained here
(perhaps someone could post the photograph from that website, since I cannot with my borked laptop). If you look at the photograph on that website, you will see that the right hand axle bearing of the freewheel type hub must be where the threads for the freewheel are. In other words, there is a lot of axle beyond the bearing which is not supported by the bearing and will be stressed by the rider weight and any bumps in the road. The axle bearing for the freehub is further along and so less of the axle is unsupported (especially so if it's a Shimano brand freehub because of their patented design).
There is therefore a much higher likelihood of the axle breaking with a freewheel hub. Hard off road use with impacts and bumps will increase the risk further. The heavier the rider the more the risk will increase too. So in your shoes I would definitely avoid a freewheel hub.
2. Disc brakes are superior in wet and muddy conditions. But I doubt very much whether you will actively seek out riding in the sort of conditions where you would consider disc brakes essential: you are a beginner, and for now all that matters is getting out for a ride for a short distance and turning the pedals. You are not going to be seeking out technical terrain or going to a designated MTB trail centre. For now you will want to ride easy non-technical safe paths and bridleways, because that is what will give you the gentle cardio exercise you need, and it's more important that you build up stamina to allow you to do that for longer rides, than trying to ride the sort of terrain where discs make a huge difference. At all costs you want to avoid incurring an injury while riding, since that may stop you riding and undo the good work you've done.
3. For similar reasons I would dismiss front suspension. As others have said it's not that great on cheaper bikes, it's added weight, and it makes fitting a full front mudguard difficult/impossible. And again, more importantly, you should not be riding terrain that is so technical (or riding it so fast), that you need front suspension, because that also means you are taking a high risk of a fall and incurring an injury.
It's possible that in a year or so's time you might have lost a lot of weight, and developed your bike handling skills and appetite for riding hard off road to the point that you would need disc brakes and front suspension, but by that point you would probably need and want a more expensive bike anyway and you would have a better idea of what you wanted. More importantly, by that point an injury would be less likely to be the sort of showstopper that it would be now while you are so overweight, unfit and just beginning to ride.
For now you just need a bike which you can ride in reasonable comfort and which won't let you down. To begin with, you will probably need to aim for very short rides, maybe even as little as only 10 minutes. Your goal is going to be to gradually build up stamina to allow you to ride a bit further each week, until you can ride continuously for, say, an hour or more. Your speed won't matter: you just need to keep going slowly and steadily and keep turning the pedals.
Too much, too soon and too fast will likely see you with an injury or in pain, and will just set you back.
As for the shoes, forget specialist cycling clothing. You just need pedals on the bike that are supportive enough for your everyday footwear, i.e. an MTB flat style pedal. Whilst some ordinary clothes are not good for cycling in, to begin with you will be riding for such short distances that the clothes won't matter. Jeans are a particularly bad choice for cycling because they are heavy, absorb a lot of water in the rain, and the seams will rub your thighs, but I still wear jeans for a short ride to the shops. Similarly cotton t shirts are not great for exercising because they hold water and can chill the rider, but that won't matter for short distances. Moreover, they are OK in warm weather. So for now you could probably get away with some everyday clothes, like 3/4 length trousers or shorts (basic clothes, like what you buy in M&S, not lycra or specialist cycling clothing) and whatever shirts/tops and jacket you already have.
If you wear nomal everyday clothing, you won't need to make a special effort to get changed to go out on the bike (because that's just an added barrier that might make the difference between going out and not going out). Moreover, you won't feel so self-conscious in normal everyday clothes, especially if you stop for a break or call into a shop or cafe. The only exception I would suggest considering is a pair of padded cycling shorts, i.e. either liners like these
or lycra cycling shorts which you can similarly wear underneath ordinary trousers/shorts, or the baggy style MTB shorts like these
. To begin with you won't need these, but as you increase time on the saddle, you may find these shorts with their trunk style (as opposed to briefs) with padding helps.