The rubrics make note of such a possibility in the Orate fratres, where it indicates in the response: Suscipiat Dominus sacrificium de manibus tuis [manibus meis], etc. This is only permitted (traditionally) under grave circumstances, e.g., in order to fulfill a day of obligation either for the priest himself or for 20 or more of the faithful, who otherwise would be prevented from assisting at Mass. As noted, the priest can say all the responses himself, though it is better to have a man (or even a woman, as the 1917 code points out) say the responses when there is no server present. If he has to say them himself, he only changes the response to the Orate fratres. Everything else is said exactly as at any other low Mass, even if no one else is present (including the blessing at the end of Mass). I suppose it would be appropriate to ring the bell, too, as this is called for by the missal and SRC decrees at least at the Sanctus, consecration, and before the distribution of holy Communion, if it is to take place. I have done this myself when I have been late for a daily Mass at my FSSP apostolate (bad traffic here…), but it’s probably better in this case simply to vest (or not… it’s not actually required for the server and wasn’t that common before the last one or two hundred years when laymen had to serve regularly, though it looks very strange to us now that we are accustomed to it) and help the priest at the altar as much as possible. It is just weird to hear the bells being rung from the nave, but I suppose the context and prudence would dictate the best solution. It is always better just to serve and do what one can (of course, there aren’t really rubrics for the server at low Mass other than kneeling for everything but the Gospels, assisting with the cruets, and making the responses). Even if the server cannot do all of these things properly, it’s better than leaving the priest by himself. It looks entirely ridiculous to see a priest at the altar alone. Perhaps some people have gotten used to it from force of habit, but it’s still quite uncalled for and contrary to the rubrics except for a grave necessity. To drive this point home, consider that it was thought to be a huge concession when St. Pius X allowed a hermit priest, who had already been living in solitude for years without the possibility of saying Mass because he lacked a server, the right to say Mass without a server.
Regarding ringing the bells three times at the elevations, I’m not sure what you meant. The missal calls for the bell to be rung three times at each elevation or continuously. The general custom is to ring the little bell at the altar three times each and the large church bells (if the church has them) continuously through both elevations. The Roman usage has the server ring the bell at the first genuflection, the elevation, and the second genuflection for each elevation. There is a very widespread French custom that has come to America only in the modern liturgical revival (outside of French colonies) to ring the bell as indicated here but then three times at the elevation, as well, making 5 times total for each elevation. This is gauche, if you ask me, and I’m not sure of its history in France herself. If it is of immemorial custom, it could perhaps be maintained, but otherwise it seems to be contrary to the rubrics.