Have you thought about a Bass Collection 5? I've just weighed my SB465 at 8.6lbs, and that has an ebony fretboard and a dense hardwood cap - a standard SB315 might get under the 8.5lb mark. String spacing is 19mm.
And lets not forget sheer dogged determination, hard graft - 600+ gigs in 2 or 3 years, sleeping on people's sofas, the underground. He's paid his dues and deserves all the success he's had if you ask me.
There are hundreds of threads about this. Generally, loops are intended for line-level (ie rack) effects. Most pedals work off instrument level and belong ahead of the dream. Just because guitarists do something does not mean it is actually a good idea - the 64 million flies argument applies.
These are great tuners for tuning the instrument, but using one to work on your intonation? I don't see how that's going to work, you need to use the tuner between your ears for that.
That bridge reminds me of something- maybe an early OLP? Should be able to pick one of those up for £150 - £200 , preferably a later one with a better bridge. Jack's right, there are far better things you could do with £230.
John Levoi knows his stuff. The FG-180 was legendary in its day for being a great sounding guitar for not much money. I think Paul Brady used to play one. If it sounds good, I wouldn't worry.
Effects loops run at line level voltage and are intended for rack and studio devices which do likewise.
Pedals mostly run at instrument level voltage and are intended to go in before the pre-amp. They may or may not work properly in an effects loop. Suck it and see.
There are exceptions: for example pre-amp pedals will usually run OK in the effects return.
The other consideration is whether you have a parallel or serial effects loop. If it's parallel, you get a blend of the clean signal and the loop signal. This might not be what you are expecting. Markbass are set up this way by default but can be changed with an internal jumper to serial.