Lou is spot on with his advice about replacing all 4 primary tires as they may have aged themselves out of service. Your 2017 trailer was purchased in 2016 and fitted with tires that could have been made in 2015. That's a 4 year run on OEM rubber. Also, believe it or not, spare tires not actively used on axles are prone to aging just like primary tires (and possibly even more so) as oils are not properly dispersed in the rubber compounds. Tires like to spin to help combat oxidation issues that lead to premature dry rot and stiffening. So replacements of all are encouraged.
I've never read that mixing steelies with aluminum alloy wheels on your two axles will have an ill-effect on tire performance. Steel wheels are often heavier and support greater load capacities tires. Tires should be of equal size and of equal load carrying capacity. That's just sound practice. Since they are "spares", there isn't any need to match all 5 cosmetically unless that's your cup of tea. I have a steelie for my spare as my primary tires are aluminum.
As far as upsizing the OEM load range tire, I would endorse that
100%. A 205/75/14 LRC tire only provides 1760# of maximum load capacity on your 7000# GVW trailer. If you were to carry 12% of the trailer's weight on the TV's hitch, that would require the tires to support a total of 6160# (1540# for each tire). When you consider an annual degradation rate of 10% for each tire, it would take just a little more than 1 year for a 205/75/14 LRC tire to be inadequate to support the full load.
As Passports and Bullets are 1st cousins of each other, I wouldn't doubt that your OEM tires are Trailer Kings. Do a search of this forum for that brand and be prepared to read a novel.
With that said, Carlisle offers a LRD tire in that OEM size. It will offer up a much heftier 2040# of load capacity at 65 PSI. If you're willing to purchase a slightly wider tire (it should fit your 5.5-6" wide wheel), Goodyear's Endurance line offers up a 215/75/14 LRD tire with an impressive load capacity of 2205# at 65 PSI. From the 3 reputable brands I researched (Carlisle, Maxxis, Goodyear), that's the highest load capacity I could find.
https://www.carlislebrandtires.com/o...adial-trail-hd
https://www.maxxis.com/catalog/tire-...t-radial-m8008
https://www.goodyearrvtires.com/pdfs/rv_inflation.pdf
If you stepped up into a 15" wheel, an LRE tire in 225/75/15 would net a whopping 2830# of carrying capacity. That's what I did with my heavier 7600# Bullet. I also upfitted my trailer with 5200# axles and springs but that a story for another day. FWIW, my OEM tires were the same size and load range as on your Passport. IMO, there's no replacement for reserve load capacity.
Finally, you mentioned having two spares for a US continental trip. That may be a little overkill as tire service centers are in abundance across much of the US. Even Walmart sells trailer tires. If I was traveling on the Alcan Highway up through the Yukon, I'd be more inclined to have 2 spares as services are sparse. But in the US, it would just be a minor inconvenience to change the flat and have it repaired or replaced soon after. YMMV.