Hi MercedesBenzo, welcome to Bluelight
If it's
you that you're talking about we prefer you just say that instead of saying it's a friend.
One thing you should know about BDD is that we are a harm reduction forum first and foremost, so we aren't really here to help you get as high as possible or more effectively abuse drugs, but to do so more safely.
So a reminder to people who reply to consider that in their responses. But we can discuss normal recreational starting doses, side effects, risks, etc.
The main thing you should know about lorazepam is that it is addictive and if you take it too often you will get physically dependent and experience withdrawal symptoms when you don't take it, which can be severe and dangerous, so please be extremely careful and restrain yourself from using this drug too frequently.
As to your questions:
Safe recreational dose: Doses are going to vary from person to person, if you are not experienced with benzos I would start with 1 mg and see how it affects you. If you take too much you will pass out or black out. You would have to take a LOT for it to be dangerous to your life UNLESS you are taking it close to other drugs, it can be
deadly if taken too close to opioids for example. Most fatal ODs are from combining it with opioids or alcohol.
Potentiators or inhibitors: I'm not really aware of any safe potentiators and there is no good reason to potentiate it, it's plenty strong on its own and you said you have a lot of it. Smoking cigarettes decreases the effects a bit, and stimulating drugs like caffeine will mask the effects somewhat. There are a couple of drugs that can decrease or increase its metabolism so let me know if you're on any other drugs.
Oral vs nasal bioavailability: The sources I have state oral bioavailability at ~85%-98% (the latter being on an empty stomach) and nasal at ~77% (and it's probably lower than that for pills intended for oral use). I would not snort it. If you want it to kick in faster you can put it under your tongue, which is listed at having a bioavailability of ~95% (for the regular oral pills when used sublingually).
Whether or not a crash is present at the end: There isn't really a "crash", since it's a sedating/relaxing drug, but you may feel groggy or experience rebound anxiety.
Drugs that it can be combined with: That is too vague, did you have any specific drugs in mind? We're not here to suggest drug combinations. I would say it's safe to combine in with cannabis. It is not safe to combine it with CNS depressant drugs, as mentioned above. It is not really worth it to combine it with stimulant drugs unless you are using it specifically to help ease the comedown from the stimulant.
Smokability and dissolvability: Don't try to smoke it. And it isn't soluble in water.