Didn't want to answer this one under hard-science tag, but considering present answer and danger of the q being closed, I can't keep silence, so on the softish side.
Practical is defined by what you have and what you want and can achieve, so, in a sense if you can 0.9c it practical in some sense as it saves time for people onboard of the craft, and it not so much practical to fly at 0.1c even to proxima (maybe practical if there is such neccessity) and even less practical and more difficult to fly at that speed to more distant stars.
But torch ship won't be able to get close to 0.9c(it can but...), and more resonable balance is indeed so often used 0.1c, and it potencially (close so) what a torch ship can do. So it your practical speed, due limitations of rocket equation
As ISM it does not have such an impact on speed limits, as sure a dust particle colliding at anything with more than 1000km/s may be problematic, but it also worth noticing that even more so it is for a dust paticle to collide with another dust particle at such speeds.
So making shield in front of the ship, by "saturating" (1-10-100x of ISM density) a cloud in front of a ship(by torch exchaust as an example, which then moves at about the speed of the ship) may be an effective mean to destroy all small particles into a plasma before ship arrives and bring that plasma to speeds closer to speed of the ship. Project orion(if I remenber correctly, or someone in reference to that project at that time) or something were proposing use of foil shreds for that - may work as well, cloud of paticles - ice grains of somehing may work as well. It should provide protection from lobe collisions so as side collisions. And it can be done in more than few ways - but it all is the same sacrificial material vs ISM, which you can constantly recycle, in that sense water ice as shield, water ice and sand, gas cloud, etc whatever it is easy to fix/deploy in the flight)
So potencially there are ways to protect caft from particles, and create warning sytem to detect things by hours ahead for big chunks which can not be destroyed by this cloud. And speed does not matter here 0.1c-0.9c it is not of much difference.
So practical velocity is defined by spacecraft capacities, what a practical space craft can achieve as a max velocity. In a sense torch ship and fusion ships are not practical for intertellar travel, but good stuff for interplanetary one. So as technologies which do not have self healing self repair properties(aka nanobots of some kind 1-2-3D nano) are not that suitable for interstellar travel.
As EVA - depends on approach, if it is a cloud infont of the ship, then space next to the ship, is quite safe and protected as km's around it
- Not downvoting because there have been scientific studies of spray, gas, and cloud shielding of spacecraft, but not upvoting because you haven't cited any of them. – @Mark
True, true. For same reason I can't comment, old browser and pad to write an answer, for same reason I didn't want to write an answerto this one, because finding links is very inconvinient on this setup.
You can edit the q and add few links, I would like to read it myself as well, maybe. As the q and a discussion of dust particles problem is not new in public discourse, and I do not see those solutions to be mentions as often as they should. I have impression that at some point it was only me pushing that idea on WB at least. I mean - I first come up with the idea writing answer or something, and then some time later I found(while researching material for some answer) a short cite mentioning proposal/connection between shred of foil and orion(or something) it was not a research work but a mentioning, I remembered it, then I even lost a link to that mentioning(I do remember as I did try years ago to find it again but without a success). I mean those solution should be 101 of space travel discourse, not forcing ppl to reinvent weels as it happened to me, but clearly they aren't, still.
So I literally forced myself to write an answer to the q, considering how not well discussed the problem and its solutions are, to which current answers are another demonstration - at time of writing a guy started to talk about energy limitations, as if the fuel does not provide enough energy, and problems of project starshot, forcing OP to invent/handwave unlimited energy sources in a hard science answer, as it fusion alone is not enough.
Further answers didn't do much better and q is about to close, so there won't be a single answer which adresses OP's clearly stated worries. @cuasative answer is somewhat exception, but his crew dies from pebble and can resist only hydrogen of ISM. For reasons I can not comment(broken javascrip for my browser) I can not upvote or downvote, or all of them would get you understand what.
So, save the planet, edit the answer or write your own if you have a chance, and add links to solutions. I hope you do not wavered once The expanse was used as an example, source, lol.