I decided to simply use the save I already have, rather than do the exploit all over again to utilise the weapon upgrade trick. 300,000 credits seems to be more than enough to carry you through the rest of the game (considering I don't have to spend any of it on power nodes, as everything is maxed out).
I just used my second save at the beginning of chapter 10, and I currently have 427,000 credits, so even with all the med packs and ammo I'm buying, I'm still accumulating credits faster than I'm spending them.
Being completely maxed out, and having the cash to buy really makes a huge difference (so far, at least). Other than a couple of rooms in which I got a bit careless, I've had no real problems. My health has only gone into the red once, but that was because I tried to rush through a particularly dangerous Stalker room in Chapter 9, instead of taking it slow. Also, whenever my health went into yellow, I'd always heal immediately, as I always have at least three med packs on me at any given time. So far I've been using the Plasma Cutter, Line Gun, Ripper, and Detonator, and not once have I ran out of ammo for any of them.
In a way, I wish I hadn't saved immediately after the exploit, as since I haven't died/restarted at all, it was technically a waste of a save point. But then, hindsight is 20/20, and although nothing has given me too much trouble, all it takes is one simple mistake, be it a particularly troublesome boss, failing a QTE or a segment where a large necromorph is holding onto you, and you have to shoot it's weak spot in time before it kills you.
To others who plan on using this exploit, it may be worth considering ploughing right through to chapter 7 (the disc swap gives you a free checkpoint), but only if you're absolutely positive you can handle everything before then on your first attempt, including all the things that can kill you instantly. You really don't want to spend another couple of hours duplicating stuff all over again.
Oh, and I also recommend using this video guide:
The guy who recorded/narrates it does ramble sometimes, but he really knows his stuff, and he has excellent advice regarding what weapons to use where, and what strategies work best in each area. Also, he gets through the game pretty quickly, so if you copy what he does, you can reduce any potential aggravation upon dying and having to retry. You should have an even easier time of it than him, as you'll have more upgrades, health, and ammo. Just be warned that there are a few places where he takes a few needless risks, and runs through areas that would be far safer to hang back in. But these are easy to spot (he even points them out himself).