A standalone unit will always be your best option for tuning. Whether or not it's "worth it" would be entirely up to you. If you're going to stay at 8lbs of boost, and you don't really need to extract the most power out of your setup and have the best reliability, then you probably wouldn't need a standalone. In addition to the cost of a standalone unit, you'd have to factor in dyno time, and paying someone to tune it, unless you feel comfortable doing that yourself, and that adds a considerable amount to your final cost.

If you want to stick with the FMU setup, then get a new inline pump. If you want to run larger injectors, depending on what size injectors you choose, you may ditch the FMU altogether, or you may just step down the FMU ratio by changing the calibration disc. You can run injectors as large as about 310cc on your stock ECM, and you would probably want to use about a 8:1 disc in your FMU with them. If you go larger than 310cc, you won't be able to idle them with your ECU, so you'll need an AFC or other device to trim fuel to idle and run them properly.

If you already have an intank pump, I would put that in, and run some DSM 450cc injectors with an AFC. With this setup, you could ditch your FMU and you won't need an inline pump. You can also get rid of whatever check valves and such you may have bleeding boost from your MAP sensor, if you stay under 10-12lbs of boost, since you'll be trimming the MAP signal to the ECM via the AFC in order to idle and run the 450s. The DSM 450s can be had for about $50-80 depending on where you go, and sometimes you can get them for even less. You'll need a resistor box or inline resistors to run them since they're peak and hold, and you'll also need OBD-I injector clips. An AFC shouldn't cost more than $300 new, and probably $200 or less used. Once it's all together, you can run a conservative base timing retard, colder plugs gapped at about .031", and get it tuned. It'll run pretty reliably, especially compared to an FMU setup, and you should be able to tune your A/F curve pretty well. In the future, if you decide on a standalone, you can simply take out the AFC, put in the standalone, and you'll already have the larger injectors and intank pump.