There are too many unknowns at the moment to really plan a strategy.
Some of your questions are relevant things to consider regardless of Trump Tariffs.
Listing on .com or .ca
Personally I list on .ca for one simple reason....it's CHEAPER, Store Fees are lower, the International fee is lower, foreign buyers pay the currency exchange if you list on .ca while sellers pay if you list on .com (unless US Dollars are useful to you).
On the other hand if you are listing in US Dollars the more the CA Dollar falls the more money you make. Contrary to that, if you are selling in CAD your prices to US buyers either keep dropping or you have more room to increase your prices. The Canadian Dollars is likely to fall at least somewhat more than it's already depressed level.
I have no comment regarding shipping included vs charged shipping, I always charge shipping as a separate line item and have no plans to every change that.
I used Chit Chats for a number of years but left due to their erratic decision making. I'm with Stallion since 2020, they provide more/better options for shipping (domestic & International), pricing overall is slightly better than Chit Chats from what I hear. Stallion opened a drop and go very close to me so I'm not switching if it means driving through Toronto traffic save pennies.
The big unknown is how the US is going to process incoming low value shipments (low value meaning anything under the old free exemption of US$800).
Scenario 1 - Shipments sent to the US via Canada Post
This would work just like buying from outside Canada, your orders enter via NY or Chicago or SF, US Customs process and applies the tariff, USPS takes over, recipient has to pay to pick up the order plus a fee similar to Canada Post. You could be seeing a lot of returns for packages never picked up, Americans really are not familiar with this paying duty and fees stuff. Big question here, will US Customs really try and collect $2.50 on a $10 order? If they do I expect the backlogs at entry points could be even worse than the classic 2007-2009 situation in Italy where months of incoming international packages built up and chaos ruled.
Scenario 2 - Shipments sent via private carriers from Canada their position as intermediaries (UPS, FedEx etc)
Customs clearance takes place at the point of entry, carrier arranges and pays for brokerage fees and duty which they then collect from buyers. Alternatively you can have these charges billed back to you (presumably you are somehow passing these costs on to the buyers)
Several issues here when shipping duty & fees paid by buyer. UPS collect on delivery but if the buyer decides not to pay the package is returned to you and bonus you get to pay for the return shipping, the original shipping, the original brokerage fees AND the tariffs that were paid. Even worse, FedEx like to just deliver the package and then bill the recipient later for the fees and duty, if they don't pay all of that will be billed back to you.
Scenario 3
Companies like Stalllion and Chit Chats, the port of entry for both is Niagara Falls, customs processing, payment of tariffs will take place there, they are not able to pass those on to the recipient like can happen when you use Canada post or a carrier like UPS Canada that controls the shipment from door to door.
Prepaying the 25% so that the buyer doesn't need to be concerned about it could be attractive to US Buyers, if this was the case it would be nice if eBay would just charge the 2.8% payment processing fee on that amount rather than the regular 13 - 15%....odds of that happening??????
There are other things that are not clear. The Canadian tariffs details clearly indicate that our tariffs will only apply to incoming items that are actually "made in the USA" as defined by our current trade agreements. Will the US do the same or will they just blanket add duty for anything shipped from Canada. There are lots of sellers in Canada who ship a mix of Canadian made, US made, plus multiple other countries that at this time are not included in this round of tariffs.
One last thing to consider, Trump loves tariffs, he also loves being able to claim victory and he doesn't need an actual victory, he just needs to be able to tell a bunch of lies that the flock believe. This whole issue could be over in weeks or a couple of months. It could also drag on for a long time, there really is no predicting when dealing with the "unstable genius". The last US President that loved tariffs was Herbert Hoover, it was one of the reasons he was elected in 1928, in spite of the historic stock market crash in '29, he went ahead with wide ranging tariffs which turned a market crash into the Great Depression which only ended with the boom caused by WWIII.
The Di Minimis exemption is ZERO as of Tuesday.
I had hoped it would be set at $100 or $200 but no such luck. I'm sure that somebody will eventually explain to Trump why spending $25 to collect $5 will not make the DOGE guy happy!
Generally speaking shipping charges as a seperate line item are not subject duty/tarrifs in any country, they are subject to VAT/GST but not duties.
In the US some States include shipping when calculating Sales Tax but on the Federal level there is no Sales Tax and shipping charges are not dutiable.
Of course if you tried to send an item declared at $1 with $1000 shipping your customs declaration would likely be reassesed based on Fair Market Value rules.
I'm quite familiar with this shipping thing because of an intensive audit by Canada Customs in the early 80's (the auditor spent two weeks going through thousands of customs entries).
I had one supplier who added an "export packing" charge to every invoice, not a big charge, maybe about 1 - 2 Dollars on each box in a shipment. I had always considered it as part of shipping and thus not included in the dutiable total of the shipment.
Customs made a ruling that is in line with this statement you posted.....
"The customs value is the price paid for the goods, including all costs up to delivery to the US" (delivery starts at the point the carrier takes possession).
.... The ruling was that the Export Packing was not part of the delivery charge because they were applied prior to being shipped and would apply regardless of how or when they were shipped.
After two weeks of hanging out in my office (really restricting our normal activities) he left with a cheque of about $600 which represented the duty evaded on 4 years worth of orders from that one supplier. This was a classic case of spending that far exceeds the amounts recovered.
Once he left we could all get back to our standard afternoon pot smoking sessions!!!!!
