Well, of course this is the crux of the whole problem! Pity that is not easy to solve.
You can't cut the military spending since you have to liberate a good part of Italy yet.
You don't have a lot of natural resources to kickstart an industry.
You can't use debt to finance industry and infrastructures since you already have a large public debt.
It's hard to attract foreign capitals, since there are several others areas who are alredy attracting them (America for example).
OTL the destra storica (translation: historical right, called so to set her apart from the XX century right movements) achieved the elemination of the public debt and build many infrastructures (railroads, roads etc...) at the price of a exsose fiscalism and a brutal repression of several revolts, like those for the tax on the flour.
A way to solve this problems could be political: have France become more powerful than OTL, to thew point that Britain decides to "groom" Italy to become a possible junior ally in the scramble for Africa and a possible war in Europe.
As for seizing the Catholic Church possessions, Franciscus, you have to consider that Italy was still largely (99%) catholic. While anticlericalism was an oblique movement that reached several classes, it was too weak to support such a move. The reaction would have been probably a series of rebelions, especially in the South. It was already difficult enough OTL, with a king de facto excommunicated...
Italy has a couple of resources they can toss in the pot: in Northern Italy the rivers can be harnessed to produce power for the industries (mainly textiles) as it happened IOTL too. There is also a skilled population that can be employed in the new factories, the infrastructures can certainly be bettered but they are not a disaster and agriculture is quite modern. What is required is some kind of vision to bring all this together asap and stable politics which would incentivate foreign capitals to come (mainly from france and Switzerland - at least at the beginning - although there were British investments in Genoa and Leghorn.
The southern part has less to offer: populace is less educated, the infrastructures are poor (although it's worth remembering that the first Italian railway was the Naples-Caserta) and agriculture is not only dominated by latifundia, but most of the owners are absent from their lands and there was not a great drive to modernise. There are a few bright points (sulphur mines in Sicily and good naval works in Palermo come to mind).
The key in the south would be to re-create a strong statal structure (the years between 1840 and 1860 were very bad years in the kingdom of Two Sicilies, with a strong reactionary backlash, an indolent king holed up in his palace in Caserta, and more interested to monitor possible plots against him than to make the kingdom grow) and avoid the OTL trap of brigandage, repression, more brigandage and more repression as well as the privileges granted to the Piedmontese industrials and traders which resulted in a net drain of resources from the south. The influence of the church is also very high, in particular in the hinterland, and any reform must be implemented with a reasonable caution. I'm not saying it cannot be done (and building infrastructures like roads and irrigation schemes would certainly produce jobs which were sorely needed) but it takes a great deal of luck and hard work as well as a strategy.