Str: grapple to be sticky. Finesse weapons may be used with str. Dwarf: cheap way to get medium armor. We don't know if multiclass is allowed. Str is iseful against abities that change your position. So you want it reasonably high.
If multiclass is allowed, wearing a shield and using protection style is not a bad idea. Uncanny dodge and protections style both use your reaction but in mutually exclusive situations. You being attacked or your friend next to you.
If tank for you means best defense and highest hp? Your suggestion is good. But if tank includes the ability to actually protect your friends with abilities othe than a body block, other suggestions are not bad. Dumping str is actually one of the worst ideas for a tank, because if you are restrained or constantly repositioned you won't be able to fulfill your job.
Grappling is nice if there is one opponent but multiples it doesn't work well. Also expertise in athletics will more than make up for a low str. As will starting in fighter for str saves, makes it hard to get pushed around or restrained. Most enemies I've encountered don't shove, or grapple/restrain. It does come up and expertise/saves will be more than enough to cover you. Needing another good/decent stat just stretches you into MaD even more. Basically my interpretation of a tank is to be enough of an issue that they cannot ignore you and last longer than they do. There are many ways to do this but the Protection fighting style is rarely a good one. You have so much vying for your reaction, you have Uncanny dodge, opportunity attacks, Sentinel
and protection? I don't think I would ever choose protection, I would much rather sneak attack the guy who just hit my friend and drop him than give a measly disadvantage to one attack.
There are very few abilites/features that actually allow you to really "protect" your friends. In Rogue he doesn't have any worth his time. Therefore he needs to play in such a way that he cannot be ignored, grappling is a decent idea but you need a free-hand for it, if you use a shield you don't have that. In my opinion the best option is being able to punish people for doing what you don't want them to do, leaving your space and attacking your friends, OA's and Sentinel achieve this, even better for him because unlike most tanks he gets sneak attack for these usually!
On the Swashbuckler vs thief, honestly Swash has a better version of sneak attack because your OA's will always have sneak. That said you lose a good amount of your out-of-combat utility. I was replying to the op saying thief, he could just mean rogue, in that case I would advise either Swash or AT, swash for sneak attacks and trickster for cantrips/utility.
The dwarf for medium armor thing is a good point, personally though I would rather go Halfling and then get the feat to gain proficiency, or just wear light armor. Usually I assume the ability to multiclass, I have very rarely heard of games where it is not allowed and I personally would never play in one :/
