Having joint symptoms where you never had any before (or only rarely) is expected when you are starting allopurionol.
But the big toe typically gets better quicker than this. Sometimes it lasts longer, especially with insufficient treatment.
2 weeks is not too soon to do a blood test but sometimes you’ve got to play along with your doctors when their ideas aren’t horribly wrong so waiting a little more for your blood test and allopurinol dose increase might make sense. But in the meantime perhaps you could see your doctor about a more effective treatment for your symptoms? Maybe you’re not taking enough colchicine. And if you didn’t get any side effects from Indocid, perhaps you could take it in addition to colchicine. The dose you took the first time wsa probably insufficient but, after being on colchicine for a while, you don’t need to take as much as would be necessary during the most acute phase of an attack and when there’s no colchicine in your system. Some doctors do not understand dosage (a gout attack isn’t a matter of life and death so they have more important things they need to know).
How long you’d need to take colchicine and/or Indocid (or similar) would depend on your symptoms. Unlike allopurinol, you can try to quit such drugs as often as you want. Worst case, you’ll get nasty symptoms.
And unlike allopurinol, these aren’t drugs you want to take every day for several months if you can avoid it (nevermind several years!).
As to the non-joint side effects you mentionned, all the investigation they might require is quitting colchicine. Colchicine has unusually strong side effects. They might even go away on their own while you are still taking colchicine.
But if they persist when you are taking allopurinol alone (or allopurinol together with a drug which has never given you such side effects), yes: I wouldn’t ignore them. Allopurinol is something you want to take for the long haul so you can’t accept the same side effects you’d accept for a drug you are only taking for a few weeks. It may be mere discomfort but it could also signal slow damage or simply a developing intolerance.
The main problem with diet is that most of the information you’ll find by looking around is worthless and that the useful information you can find isn’t comprehensive. When people aren’t told what reduces UA in the first place, naturally they will fail to achieve results.
Sticking to a diet tailored to lower UA isn’t very hard as long as you’re not an alcoholic. Giving up animal flesh is as easy as finding something else you like to eat. It might take some time (obviously you can’t simply yank something nutritious out of your diet without making other changes!) but it’s much easier than losing weight for instance (though losing weight is in some cases the main thing you’d need to do to lower UA!).
I wouldn’t overly concern myself with diet in your situation. You’ve already started allopurinol which works much better than diet. Some things still matter because they complement allopurinol but you’ll most likely be fine if you simply eat a healthy diet (with veggies and stuff) and avoid alcohol as well as other diuretics.
X-rays would only show something after years of pretty serious gout. MRIs are as I understand it not very specific (you wouldn’t ID crystals). Ultrasounds (is that the right word?) is another option which only shows the effects of crystals. Synovial fluid is very specific (it even discriminates between types of crystals) but hard to do correctly so can yield false negatives. I wouldn’t rely on any of these to guide treatment, only for diagnosis.
What works best apparently is DECT scans but that’s fairly new and not many gout sufferers can get them. That’s the one thing (besides blood tests) which could guide treatment effectively.