So it looks like your uric acid (not acidity!) is only occasionally too high for a gout sufferer. That means allopurinol is probably not necessary (or at least not necessary yet).
Recently, your weight loss diet with reduced carbs probably contributed to the problem but perhaps you used to have a different diet or lifestyle which gave you gout 5-10 years ago. Now that you have lost weight, it may be possible to use less dangerous remedies than allopurinol to keep your uric acid down. The most common foods people take to reduce uric acid are probably milk (or yogurt) and cherries. Avoiding meat or fish (or at least reducing the amount you eat) is also key to keeping your uric acid in check if you don’t take allopurinol.
One urine’s acidity (not uric acid!) is more complicated than a single number out of context but a pH of 5.5 does suggest as I suspected that your diet might be deficient in minerals (specifically: calcium, magnesium, potassium). I would recommend eating more mineral-rich food such as most whole fruits and vegetables every day rather taking supplements or baking soda. It’s not uncommon for elderly folks to need to watch their urine’s acidity so you should be able to get advice from doctors and dieticians about this or your could look at food databases for yourself. A less acidic urine would help your kidneys and in particular help them to get rid of the uric acid in your system.
Note that all the dietary tweaks I mentionned would only help over the long run by preventing gout and the damage it causes. They are not quick fixes for when you’re in pain.
If you need to use baking soda when you’re in pain, fine. But perhaps you could also consider other anti-inflammatories than the ones which have caused you trouble. For instance (and depending on where you hurt) you could perhaps try a local (topical) anti-inflammatory rather than a pill. There’s also colchicine.