I am so sorry you are going through this.
What you describe is very similar to how I discovered my H affair/s.
I tried snooping and had some successes and some fails. I too could not access certain accounts online due to lack of passwords. I did have some success though.
If you wish to continue snooping then all I can suggest is what I did and where I looked and some of these did hold further evidence. Like you I could not fathom where in the day H could find the hours to see anyone else but my digging further it seemed he was not working quite as many hours as I thought and that it was not an affair he was having but sex with random women chatted up online. In other words he could have a quick shag in his lunch break or on the way home from work because there was no dating/chatting up in RL involved - all that had been done online so when he met up with these women it literally was for pre arranged sex - he could be in and out within an hour. Shocking yes and I am not saying this is what your DH is doing but explaining that "no spare time for an affair" like I initially thought can be something no too good.
I unconvered various bits of evidence by going through his stuff, car etc with a fine tooth comb. Some stuff I found on their own meant nothing but when eventually peiced together - added up. I search pockets, not just pockets of the clothes he wore that day or day to day but every single pocket of every item he had in the wardrobe. Inside an old suit pocket not worn for years I found a mobile phone charger (later found to be for his shag mobile - as I called it).
Other places were his car - Behind panels of the door, under the carpet - in the rear light cavity on the boot I found a stasch of condoms.
I started keeping a note of days and times. I checked the mileage on the car, bank statements and reciepts. A petrol receipt also confirmed something else I had found. Look for cash withdrawals - is he buying petrol at a different petrol station to usual, not quite on his way home etc etc.
I snooped over a period of weeks and at the end of it had alot of evidence but still huge gaps. I could not carry on snooping - I was making myself ill. So I do not recommend doing this long term - maybe you can gain something from my search tips if it helps, but with you feeling so stressed take care of yourself and know when to stop.
Other places I looked included the loo cystern, behind bath panels, his workbench area of the garage and event the attic.
I would think long and hard about how you will confront him. I personally don't think laying all your cards in the first instance is the way to go. You only have to read any "I think my DH is having an affair" thread on here to see that those that do come away with more questions and doubt than those that hold back.
In my case (and many others on mumsnet) he will usually deny initially then only admit to what he thinks you know. I call it "operation damage limitation" on behalf of the cheating husband. Confront with snippets but dont explain your sources, let him speak. Its hard and its hurtful. I probably still dont know ALL of my H infidelity and fact surrounding it. I discovered a fair bit myself and he told me more - by my careful questioning and forcing facts out of him by confronting with evidence. Few men lay their cards fully on the table. But I knew when enough was enough - the rest didnt matter (except my sad obsession to know) - the line had been crossed for our marriage and that was that.
My experience is based on the fact my H was cheatuing. Ofcourse - your may not be - although some of what you say needs explaining.
Hope I have not bored you - was trying to give you some support and tips.
Hugs OP - hope its not as bad as it seems right now.